I. '08. 134 



Family CRANGONIDAE. 



The number of British and Irish species of Crangonidae has 

 been nearly doubled since Bell in 1853 wrote his British Crus- 

 tacea. Kinahan's treatment of the family eight years later is 

 very inadequate and his figures are most misleading, while the 

 other literature is much scattered. Short descriptions of each 

 species are therefore given here, and these, taken in conjunc- 

 tion with the figures, should afford a ready means of deter- 

 mining the various forms. 



The confusion which exists among the genera of this family 

 must have struck the most casual observer, yet the question is 

 in reality very simple, for the whole difficulty may be traced to 

 the incorrect application of Guerin-Meneville's Aegean. Such 

 species as echinulatiis, trispinosus, sculptus, fasciatus, neglec- 

 tus and hispinosus have all at various times been referred both 

 to it and to Cheraphilus , and some also, with less reason, to 

 PontophUns. An examination of cataphractus , the type species 

 of Aegeon, at once shows that none of them should rightly be 

 referred to that genus. A. cataphractus has deep sculpture and 

 spinous ridges on both carapace and abdomen, the first pereio- 

 pod bears a setose exopod, the endopod of the last four pairs of 

 pleopods is nearly as long as the exopod and bears an appendix 

 interna at its base and the inferior apices of the branchiae 

 point forwards, giving them a most characteristic C-shaped 

 appearance, which may be at once seen on raising the gill 

 cover. None of these features are present in the six species 

 mentioned above, but the question still remains w^hether tw^o 

 genera may not be represented among them. In this connec- 

 tion Gurney's researches on laval Crangonidae (1903) are of 

 great importance. He examined the larvae of eight species, 

 and found them to fall naturally into three groups, which he 

 thus defines : — 



" 1.— Vulgaris and Allmanni : characterised by a one-jointed 

 maxilla-palp and the absence of an exopodite on the 

 second leg in the my sis stage. 



"2. — Trispinosus, nanus ( = hispinosus), echinulatus and 

 fasciatus ; characterised by their two-jointed maxilla- 

 palp, possession of five pairs of exopodites in the 

 niysis stage, form of the rostrum and arrangement 

 (paired) of the abdominal spines. 



" 3. — Spinosus and norvegicus : distinguished from the 

 second group by their extremely elongate body form, 

 shape of the rostrum, possession of a long median 

 spine on the third abdominal segment, and by the 

 form of the tail plate." 



Group 1 is the genus Crangon and group 3 Pontophilus. 

 Group '2 combines species which have been referred both to 

 Aegeon and to Cheraphilus. Gurney therefore called it by the 

 former name, which had the advantage of priority. This, as I 

 have shown above, is due to a misconception of the characters 



