THE SOUTH AMERICAN NEMATOGNATHI OF THE MUSEUMS AT LEIDEN AND AMSTERDAM by J. W. B. VAN DER STIQCHEL (Museum voor het OnderwSs, 's-Gravenhage) The collections of the South American Nematognathi in the Rijksmuseum van Natuurlijke Historie at Leiden, referred to in this publication as "Mu• seum Leiden", and of those in the Zoologisch Museum at Amsterdam, referred to as "Museum Amsterdam", consist of valuable material, which for a very important part has not been studied yet. I feel very much obliged to Prof. Dr. H. Boschma who allowed me to start with the study of the Leiden collections and whom I offer here my sincere thanks. At the same time I want to express my gratitude towards Prof. Dr. L. F. de Beaufort, who has been so kind to place the collection of the Zoological Museum at Amsterdam at my disposal. Furthermore I am greatly indebted to Dr. F. P. Koumans at Leiden for his assistance and advice to solve the various problems which I met during my study. The material dealt with here comes from a large number of collections of different collectors, from various areas of South America, it consists of 125 species, belonging to 14 families of the order Nematognathi. Contrary to the original expectations no adequate number of specimens from Surinam could be obtained to get a sufficient opinion about the occurrence of the various species, and, if possible, also about their distribution in this tropical American part of the Netherlands. On the whole the collections from Surinam were limited to the generally known species only. Pygidium gracilior Eigenm., hitherto not known from Surinam, forms an exception in this respect. Out of the 125 species described in the present paper only 41 originate from Surinam. At the beginning of Bleeker's (1864) investi• gations of the Nematognathi in the collections of the Museum Leiden and the Museum Amsterdam, there were 23 species from Surinam. During his work, however, he increased this number with 21 species. The additions of 7 newly founded species by Bleeker must be cancelled, because of their -Zoologische Mededeelingen XXVII i 2 J. W. B. VAN DER STIGCHEL being synonyms of already classified ones. In Bleeker's time therefore 37 species from Surinam were present in the collections. This number since has been increased with 4 species, which means that an important task for investigators is still to be accomplished. From the literature I could collect the particulars of 50 species from Surinam, 35 from French Guiana and 48 from Demerara. The expedition to British Guiana, led by Prof. Dr. C. H. Eigenmann (1912), collected 76 species of Nematognathi. I must, however, draw attention to the fact that among the stated totals the species mentioned therein are partially different from those referred to above. As Surinam belongs to the same geographical area as those above mentioned, the presence of the same spedies as in the said regions may, to a certain extent, be expected. It is a matter of fact that a more intensive way of collecting than at present was possible would yield a great number of species of Nemato• gnathi from Surinam, which until now have not yet been recorded for the country. When in the statements of the studied species nothing is said about the preservation, they are preserved in alcohol. Stuffed specimens are specially, mentioned. The names of the localities are given as written on the labels and checked according to Stieler's Atlas. In cases, where these names wanted correction or where in any way they were liable to comment, it is to be found in the description of the specimens. FinaJly I wish to thank Mr. P. van't Zelfde for the figures of the new species. Various species of the order Nematognathi have already drawn attention of investigators of the South American fauna. There are figures and more or less good descriptions by the pre-Linnean authors Marcgravius (1648), Willoughby (1686), Gronow (1754) and Seba (1758). In a very limited number of cases is it possible, with their plates and descriptions, to find out with which of the now known species those can be identified. The figure of the Bagre de Rio of Marcgravius (1648), for instance, represents Rhamdia quelen (Quoy & Gaimard), and the animal named by this author Bagre without any doubt is Pimelodus clarias (Bloch); the Oipbagre probably is Franciscodoras marmoratus (Reinhardt), whereas the Tamoata undoubtedly is Callichthys callichthys (L.). I have every reason to state this on account of certain typical characters of the figures. The descriptions are totally unadequate. Willoughby (1686) copied these figures and descriptions unaltered. SOUTH AMERICAN NEMATOGNATHI 3 Gronow (1754) came forward with an important improvement by giving detailed and accurate descriptions, in some cases even with measurements. The figures themselves are more accurate. Moreover, he classified forms with corresponding characters in separate genera. Seba (1758) gives very accurate figures; his descriptions, however, although rather detailed, are incomplete. Under the names Mysti, Barbeau or Barbu he brings together all the forms that have barbels, so, besides the Nematognathi, this group includes some fishes of other groups too. He divides them into two classes: I. Cauda bifurcata et appendice cutacea in extremo dorso. II. Mysti cauda in extremo vel aequali, vel levissime bifida, quorum alii appendice dorsali gaudent alii carent. Linnaeus (1758, 1766) included in the order Pisces Abdominales under the genera Silurus and Loricaria all forms of the group known to him. Bloch (1794) separated from the genus Silurus a genus Platystus; so he consequently had 3 genera, viz., Silurus, Platystus and Cataphractus = Callichthys L. Lacepede (1803) classified 15 genera, of which 8 were of South Ameri• can origin, viz., the genera Silurus, Pimelodus, Doras, Cataphractus = Callichthys, Ageneiosus, Loricaria, Hypostomus = Plecostomus, and Corydoras. Mitchill (1814), Von Humbolt (1806), Lichtenstein (1829), Jenyns (1842), Temminck (1845), Mujler & Troschel (1845), Schomburgk (1848), Kner (1853, 1858), Castelnau (1855) and Gunther (1864) united all forms of the group known to them, in the family Siluridae. Agassiz (1829) did so too, though he already stipulated that the char• acters of some genera had the value of family characters. As a consequence he created a separate family Goniodontidae. It was Bleeker who introduced important modifications in the systematics of the group by creating the order Siluri, which in 1858 he divided into 4 families, the number of which in 1863 he augmented to 6, viz., Loricarioidei, Callichthyoidei, Siluroidei, Aspredinoidei, Chacoidei and Heterobranchoidei. Gill (1870) replaced the name of the order Siluri by Nematognathi, of which Cope (1870) gave the following definition: "Praecoracoid arch present. No coronoid or symplectic bones. ParietaJs and supraoccipital confluent, four anterior vertebrae coossified, and with ossicula auditus. No mesopterygium. Basis cranii and pterotic bone simple, third superior pharyngeal bone wanting, or small and resting on the fourth, second directed backward. One or two pairs of basal branchihyals, two pairs of 4 J. W. B. VAN DER STIGCHEL branchihyals. Suboperculum wanting, premaxillary forming mouth-border above. Interclavicles present." Cope divided the order into 3 families. Gill (1872) changed this division altogether and introduced 11 families. Eigenmann & Eigenmann (1890 b) added to these 11 families that of the Diplomystidae. Eight out of these families occur in tropical America only. Four of them are subdivided into a number of subfamilies. This classification by Eigenmann & Eigenmann (1890 b) was considered as being to a certain extent provisionally; although in Eigenmann's later publications he adhered to this system. In 1925 he promoted all subfami• lies, with the exception of the Loricariidae, to families without any further explanation. It is true, indeed, that the value of the characters, which led to the classification of subfamilies is of sufficient importance to warrant a division of the Nematognathi into 16 families, 14 of which are represented in the collections described in the present paper. The key to the 14 families, of which specimens are described in the present paper, gives the explanation why the chosen division is the most logical. The important morphological and anatomical differences between the Ariidae, Callophysidae, Pimelodidae, Auchenipteridae, Ageneiosidae and Doradidae render it impossible to include these as subfamilies in the family Siluridae. When I started to divide the family Doradidae into genera I followed the thoroughly altered system given by Eigenmann (1925), which strongly differs from that given by Eigenmann & Eigenmann (1890 b) and that used by Eigenmann (1906 and 1912). The division into genera according to this system is based on a number of anatomical characteristics, viz., the exag• gerated development of the parapophyses of the fourth vertebra, asso• ciated with the peculiar air-Madder and Weberian apparatus." This system in almost all respects runs parallel with that of Bleeker (1863 b), whose system is totally founded on morphological characteristics. From Eigen• mann's use of anatomical characters one may notice at once that the'old division can be considered to be exact. Eigenmann has even added a number of new genera. I could increase the number of species of the genus Megalo- doras with a new one, which I named Megalodoras paucisquamatus nov. spec, on account of the small number of scutes in the lateral series. The foregoing plainly shows how essential a minute comparison of the anatom• ical characters is to confirm the results of the morphological analysis. It is to be regretted that I could not do a thorough research in more genera because the limited number of specimens of each species did not justify the loss connected with anatomical analysis. Under the circumstances I have tried to define the limitations of the SOUTH AMERICAN NEMATOGNATHI 5 species as accurately as possible by availing myself of the data of a num• ber of essential coefficients.