210 of Rhode Island, 1965 ) . Schroeder obtained trawl catches of up to 245 crabs per hour's fishing in the waters off the coast from Nova Scotia to Virginia; the best catches were made between 150 and 550 fm (274 and 1,005 m). The crabs were mostly large, measuring 4 to 51/2 inches (102 to 140 mm) across the carapace, weighing up to 2 Ib (0.91 kg) or a little more and yielding up to 4 oz (113 g) of meat. The meat is said to be delicious. Further search by trawl in the deeper waters off the European coast might well disclose the existence of exploitable con- centration of Geryon affinis there.

REFERENCES

GORDON,I., 1956. Paromola cuvieri (Risso), a crab new to the Orkneys, Shetlands and Norway. Nature, London, 178: 1184-1185. HANSEN,H. J., 1908. Crustacea Malacostraca I. Danish Ingolf Exped., 3 (2): 1-120. KJENNERUD,J., 1967. A find of Geryon affinis Milne-Edwardsand Bouvier, 1894 (Crustacea Deca- poda) off the coast of Norway. Sarsia, 29: 193-198. MASON,J. & DAVIDSON,C., 1966. Cancer bellianus Johnson in northern Atlantic waters (Decapoda Brachyura). Crustaceana, 10 (3) : 318-320. MILNEEDWARDS, A. & BOUVIER,E.-L., 1894. Brachyoures et anomoures. Crustacés décapodes pro- venant des campagnes du yacht l'Hirondelle (1886, 1887, 1888), I. Résult. camp. scient. Monaco, 7: 1-112. �& �, 1899. Crustacés décapodes provenant des campagnes de l'Hirondelle (supplement) et de la Princesse-Alice(1891-1897). Résult. camp. scient. Monaco, 13: 1-106. RAE, B. B. & LAMONT,J. M., 1963. Rare marine invertebrates found in the Scottish area. Scottish Natural., 71 (1) : 23-28. REES, G. H., 1963. Edible crabs of the United States. U.S. Bur. Comm. Fish., Fishery Leaflet, 550: 1-18. SCHROEDER,W. C., 1959. The lobster, Homarus americanus, and the red crab, Geryon quinquedens, in the offshore waters of the western North Atlantic. Deep-Sea Research, 5: 266-282. UNITEDSTATES BUREAU OF COMMERCIALFISHERIES, 1962. Gulf exploratory fishery program. Comm. Fish. Rev., 24 (10): 19-20. UNIVERSITYOF RHODEISLAND, 1965. Economic and marketing study of deep-sea red crab under- taken. Comm. Fish. Rev., 27 (1) : 26-27.

NAMES OF LARVAE IN THE DECAPODA AND EUPHAUSIACEA

BY

D. I. WILLIAMSON Marine Biological Station, Port Erin, Isle of Man, British Isles

Post-embryonic development in the Decapoda and Euphausiacea consists of a series of stages, separated by moults. Some of these moults involve little change of form or habit, and the stages linked by them may be grouped together as a 'phase' in development. The phases are nearly always separated by one moult, involving some major morphological change (metamorphosis) and frequently a marked change in behaviour. 211

Gurney (1942) emphasized that the primary division of the stages into phases should be based on the method of swimming, and he named and defined the phases which he recognized thus:

In an identification sheet, published in 1957, I included a modified form of this classification, in which the protozoeal stages were included in the zoeal phase and in which the term 'megalopa' was applied in a broad sense to replace Gurney's use of the term 'post-larval'. There was no opportunity at that time to explain these modifications, but subsequent published comment and correspondence has shown that some amplification is desirable. The purpose of this note is, there- fore, to explain my modifications to Gurney's system and the need for them. There is general acceptance that a nauplius is a larval crustacean, lacking com- pound eyes, in which the first three pairs of cephalic appendages are all natatory and no other appendages are functional. The term 'metanauplius' is often applied if other developing (non-functional) appendages are present, but it is a con- venience to use 'nauplius' in a broad sense to include 'metanauplius'. Free naupliar stages occur in the development of the Euphausiacea and the Penaeidea but not in other groups of the Eucarida. Zoea Bosc, 1802 (fide Gurney, 1942) was originally a generic name, applied to what was later shown to be a larval brachyuran. Its use has, however, been extended, until it its broadest sense it includes all larvae of the Decapoda and Euphausiacea with natatory thoracic exopods and in which the pleopods are absent or non-functional. Gurney (1942) argued convincingly for the adoption of the term 'zoea' in a relatively broad sense both because of the desirability of being able to use the same name for comparable larvae of any group and because of the difficulty of framing a satisfactory definition which would apply the term in a restricted sense. Even if it were practicable to restrict the term to brachyuran larvae this would be extending a generic name to cover a group usually regarded as a section, and it would include a wide variety of form. The law of priority is not strictly applicable to the naming of developmental phases, but the fact that 'zoea' is the oldest name to be used for any larva in this phase is a point in its favour. My use of 'zoea' agrees with Gurney's in including larvae which have been termed metazoeas and mysis or schizopod stages; it differs in including protozoeal stages, which were specifically excluded by Gurney. The term 'protozoea' is applicable to the first three post-naupliar stages in the Penaeidea and the Euphausiacea, although some authors have restricted it to the first two such stages. In the Euphausiacea the name 'calyptopis' has more usually been employed, but there is no essential difference from the penaeid protozoea. In such a larva the carapace is developed but not fused to the thorax; the thorax