538 CRUSTACEA MALACOSTRACA. 



with reduced pleura. Eye stalks short, 1st pair of trunk-legs powerful, 

 ending in chelae of which one is larger than the other, 3rd pair never chelate, 

 the last pair directed backwards ; uropods usually large. Branchiae often 

 reduced in number, filamentous, and in some cases, foliaceous. An 

 appendix interna usually present on the abdominal endopodites. The 

 larvae hatch as zoaeae (except Eiconaxius q.v.) and pass through a 

 mysis stage, having, in accordance with the adult structure, an intermediate 

 character between the zoaea larvae of the Caridea and the Anomura. 

 Some superficial resemblances between the adults and the Stomatopoda 

 are interesting from the similarity in the mode of life of the two groups. 

 They have been divided into four families, which are however closely 

 related. These are differentiated as follows.* 



I. Fam. 1. Axiidae. No linea thalassinica. Both movable (scapho- 

 cerite) and fixed thorns f of 2nd antennae present, though sometimes 

 minute (? in Scytoleptus). Abdominal pleura large. Axius Leach. 

 Scaphocerite scale-like. A. stirhynchus Leach. British and French 

 coasts. In the sub-gen. Eiconaxius, from deep water in the Pacific, 

 Spence Bate found that the young in the egg had all the limbs of the adult, 

 except the first abdominal, the 3 last trunk-legs being biramous ; Axiopsis 

 Bor. ; Calocaris Bell, last thoracic segment covered by the carapace, 

 scaphocerite may be much reduced. Chelae not markedly unequal. 

 Deep water forms. The eyes are developed, but the pigment is reduced 

 or 0. C. macandreae Bell, Great Britain, Ireland, Norway. The zoaea 

 larva has well developed eyes, and 3 swimming maxillipeds, as in Caridea 

 (G. O. Sars). Scytoleptus Gerst. 



II. Linea thalassinica present (except Callianidea). Fixed antennal 

 thorn wanting. Scaphocerite reduced to a flattened vestige or 0. Ab- 

 dominal pleura usually small. 



(1) Fam. 2. Laomediidae. Sutures on both endopodite and exopodite 

 of uropods. Abdominal pleura of good size. Laomedia de Haan ; 

 Jaxea Nardo ; Naushonia Kingsley. 



(2) No sutures on the last limb. Abdominal pleura small. 



(a) Fam. 3. Callianassidae. Carapace laterally compressed ; rostrum 

 minute or 0. Scaphocerite vestigial. Second trunk-leg chelate or simple. 

 Gills filamentous. No podobranchs on trunk-legs ; abdom. legs 36 

 broad, uropods without suture. Callianassa Leach, swimmerets 3-5 

 broad and large. Some 18 spp. C. subterranea (Montagu), British. 

 Olypturus Stimps. Callianidea M. Edw. swimmerets 2-5 very large and 

 fringed with silky, articulated hairs. Western Pacific. Upogebia Leach 

 (Gebia Auct.), 1st trunk-legs subequal and subchelate, swimmerets 2-5 

 large. U. stellata (Montagu), S. Devon, U. littoralis Risso, Mediterranean 

 and Norway. Development studied by Sars who finds that the 3rd 

 maxilliped is not present as a swimming appendage in the zoaea stage. 

 Gebicula Ale. ; Bigea Nardo. 



(b) Fam. 4. Thalassinidae. Carapace dorsally flattened, with rostrum ; 

 scaphocerite ; 1st and 2nd trunk-legs subchelate ; abdominal appendages 

 including uropods slender ; branchiae filamentous and foliaceous ; podo- 

 branchs on trunk-legs 1-3. Thalassina Latr. T. scorpionoides Latr. 

 Pacific. 9 in. long. 



* Cf. Borradaile, Classification of Thalassinidea. A. and M. N. H., 1, 

 vol. 12 (1903), p. 534. 



f The fixed thorn is an external process from the 2nd segment of the 

 antenna. 



