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The malacologicalsocietymalacological society ofJapanof Japan 70 VE}.i(. (J.S.E. -22-(-i.? i96L2- 1.ll 1sclll!T a =?- ;if d FP cD f{.ir EI], lc mavg' 6an 3{i (1) ',et,!i. ]li kt: ):fiStr JIIk!R./iZffE,)cklkS･"i A Study on the Radu!ae of the Japanese Muricidae (1)* ----The Genera PurPwra, Thais and MancineUa- Kohman Y. ARAKAwA Miyajima Aquarium, Hiroshima, Japan (]S<IKtSi Pls. 5-6) The present study was carried out in my student life under the guidance of the late Dr. Isao Taki, the former curator of zoology in the National Science Museum, Tokyo. I expected to go on with the study and to publish the results in a more complete form, but for certain reasons the pursuit of the work in the same course has been laid aside for years, hence I intend to publish the results, so far as gained, on the occasion of the memoria1 number for h is death. Acknowledgements are due to the late Dr. Isao Taki for his kind guidance and encouragements rendered to me during my stay in the Museum and to Dr.library.Tokubei Kuroda for his generosity in offering me to refer to- his private Thanks are also extended to Dr. Tadashige Habe who read the ma- ' nuscrlpt and gave me valuable advices and criticisms in the course of the study. "PzvrPztra" Aarenumber of species which have been referred to the genus reported to occur in the Japanese and her neighbouring waters. They are-regarded as carnivorous, generally making a prey of other animals of their own phylurn. Adapting themselves to the feeding habits, all of them possess rather strong rachiglossate radulae which are formulated in 1-C-1. The radulae have multicuspidate rachidians with cusps varying three to five in number according to species and roughly crescent-shaped laterals which show no clear-cut distinction among the members of the genus. From a conchological point of view, the precise limits of this genus have been somewhat ill-defined and confused on account of the extensive variation 'Contributions from the Miyajima Aquarium Laboratory, No. 10. t'.i [Z S; ,'j LLI'i.I71 Er l;G zi<1tc re tiJFYti jte{ f}"t ."ta'Y ] O NII-Electronic Library Service The malacological society of Japan ･Japanese ARAKAvvA: Radulae of Muricidae (1) 71 in the shell forms. But the members of this genus are subdivided into three distinct groups based chiefly on the characterisitics of the rachidian teeth of the radulae as follows: Group 1 ---Rachidian Radula. tooth 5-cuspid and ornamented with strong comb- toothed outer denticles on the outside of the lateral cusps; marginal cusps prominent and sharply pointed at its tip: base broad. ---Persica Species. Linn6, Panama R6ding Group 2 Radula.- Rachidian tooth 5-cuspid and furnished the outside of the lateral cusps with small saw-toothed outer denticles: marginal cusps not prominent and rather obtuse: base broad. ---armigera 'clavigera Species. Link, bromti Dunker, bzffu Lamarck, Lischke, distingztenda Dunker et ZelebGr, echinata Blain- ville, hiPPocastanum Linn6, luteo.stoma }Iolten, Pseztdodia- dema Yokoyama Group 3 Radula. Rachidian tricuspidate and devoid of marginal cusps; outer denticles absent; base narrow but rather massive. ･ Species.-echinulata Lamarck, intermedia Kiener, mancineUa Linn6, lata Kuroda, siro Kuroda, tz･eberosa R6ding Besides, the following five spec{es that have been referred to this genus are known to occur in our territory. But nothing has been reported with regard to their radular characters up to the present so far asIam aware. rngosa Born, mzaltilineata KUster, squanzosa Pease, jovanica ? Phi- "zutabilis. lippl, Link . From the result of dissection of the radulae, it is evident that the groups 2 and 3 are not cengeneric with the genus PzarPura (group 1) be ¢ ause of showing no agreement with those of PurPma in radular characters. I pro- pose, therefore, the group 2 should be placed to the genus Thais in having the 5-cuspid rachidians with saw-toothed outer denticles as those of Thais- tyPe, .not of Parpm-ra, while the subgenus Mancinella (group 3 ) should be NII-Electronic Library Service The malacological society of Japan 1, 72 1962 ..V..E!ilUS: 22 (1) given generic rank in view of the very rnarked differences between these radulae and those of PurPztra. The detailed descriptions and figures of the radulae in the members of PurPura, Thais and Mancinella are here given. Genus PurPura Brugui6re 1789 Type, BuccimtmPersiczimLinn6 "Thais " The description and the figure of the radula in Persica L. was given briefiy by Cooke (1918) in the followings: "Central side cusp long and broad; cusps small but conspicuous, two-thirds way down; outside, 4-･5 strong deeply-cut denticles, one '' of which climbs; knob large and elevated. I'ztrPetra Panama (Roding) (== rudolPhi Lam. ) (Pl. 5, fig. 1) The rachidian tooth is 5-cuspidate on the broad base; .the central cusp is rather thin and narrow but sharply pointed at the tip, which reaches appro- ximately 1.7 times as long as the lateral cusps; the lateral cusps are recurved posteriorly; a large inner denticle is set at one-third way up on the inside of the lateral cusps; on the outside, there are four long outer denticles which show, on the whole, an appearance of the teeth of a eomb; the marginal cllsps are conspicuous and sharply pointed at the tip; the base is broad, roughly rectangular in shape and waved below. The lateral teeth are cres- centshaped in outline and show the common features with those of other members of the genus. Genus Thais ROding 1798 Type, 1-kais lena R6ding=Mzerex fusezas Gmelin==Nerita nodosa Linn6 ``Thais The radula o ± nodosa L. (PitrPura neritoidea Lam. )'' was illus- trated by Troschel (1869) in his Das Gebiss der Schnecleen (Bd. Ili, Taf. XII, fig. 12.). Thais armigera (Link) (Pl. 5, fig. 7) The rachidian tooth has five main cusps set on the broad base. The central cusp fianked by two small lateral cusps is rather thick and strong; the lateral cusps ceme up approximately two-thirds of the length of the central cusp; one small inner denticle is located at one-third way up on the inside of the lateral cusps; on the outside, five or six small outer denticles are serrated like the NII-Electronic Library Service The malacologicalsocietymalacological society of Japan ARAKAwA:. Radulae of MuriEidae.(1> 73 Japa.n. -e.se teeth of a saw, one of which is high up along the outer margin; the marginal cusps are small and blunt at the tip; the base is broad and singly arched below. The lateralsare common to those of other species of the genus. Thais bromti (Dunker) The central cusp is long and sharply pointed, but is not so thick as that of the above species. It attains about two times as long as the lateral cusps; the lateral cusps turn feebly outwards and are prbvided with a large inner denticle on the inside; the area intervening between the lateraland the mar- . ginal cusps are ornamented with six or seven small denticles, some of whlch climb up on the outside of the lateral cusps; the marginal cusps with a blunt are recurved tip weakly outwards; the base is broad and curved slightly below. ' Thais distinguenda (Dunker et Zelebor) (Pi. 5, figs. 2--4) The rachidian tooth possesses five main cusps; the central cusp is rather strong, thickened at the center and arched posteriorly; on eithei side of the central cusp, the similarly shaped lateral cusps flank directing upwards in the anterior view, which reach about three-fifths of a length of the central cusp; a large inner denticle is situated one-third way up on the in$ide of the lateral cusps; on the outside, there are three deeply-cut outer denticles; the marginal cusps are small and bluntly pointed at the tip; the base is roughly rectangular in shape and fiattened below. Thais hiPPocastanienz'gLinn6) leieneri (r=- Deshayes) The rachidian marked cusps on tooth has five the basal plate; the central cusp is the thickest and longest of all the cusps, and is flanked by two lateral cu.q.ps which are recurved feebly outwards and reach nearly half a length of the central cusp; the lateral cusps are provided with a large inner denticle which is upright and climbs half way up on the inside; the spaces between the lateral and the marginal cusps is serrate with four outer den- ticles, one of which climbs rather low down along the outside of the lateral cusps; the marginal cusps with an obtuse tip are very small and turn weakly outwards; the broad base is flattened at the both ends and arched below. Thaislzateostoma(Helten) (Pl. 5, fig. 5) The rachidian tooth has a long and sharply central cusp which pointed NII-Electronic Library Service The malacologicalsocietymalacological society of Japan IP62- 74 VENUS: 22 .(1}. attains abctut two time$ as long as the lateral cusps; the lateral cusps are rather short and thick, and turn outwards; one small inner denticle climbs about half way up on the inside; the four denticles are serrated on the out- side, one of which climbs low down; the marginal cusps are small and obtuse; the base is broad and slightly arched below. laterals are nearly crescent in outline with a broad base. The . Thais Pseadodiadema Yokoyama (Pl. 5, fig. 6) . species shows a close similarity in its radular characters to The present that of the above species. The rachidi,an tooth is roughly triangular in outline and 5-cuspid on the broad base; the central cusp is long and sharp, and is fianked by two short $imilarly shaped lateral cusps; the lateral cusps which attain half a length of the central cusp are slightly inclined outwardly; one small denticle climbs half way up on the inside of the lateral cusps; the marginal cusps are very small, not conspicuous and obtusely pointed at the tip; four small denticles intervene between the lateral and the marginal cusps, one or two of which are slightly high up along the outside of the lateral cusps; the base is broad and singly curved below.

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