256 



THE CRUSTACEA 



FIG. 145. 



Carapace of the Norway Lobster (Xephrops nor- 

 vegicus) from the side. (After Boas.) The letters refer- 

 ring to the grooves of the carapace are those used by 

 Boas, e, e,', the "cervical groove " of Bouvier, "anterior 

 cervical groove " of Borradaile ; c, " branchial groove " 

 of Bouvier, " posterior cervical groove " of Borradaile. 



carapace have been studied by Boas and by Bouvier. Only a few 

 points can be mentioned here. In the lobsters and crayfish a con- 

 spicuous groove (Fig. 145, c) crosses the dorsal surface of the 



carapace transversely about 

 the middle of its length 

 and curves forwards on 

 either side. This groove, 

 named the " cervical groove " 

 by Milne - Edwards (c in 

 Boas's terminology, the 

 " branchial groove " of Bou- 

 vier), was supposed by him 

 to indicate the line of 

 division between the por- 

 tions of the carapace aris- 

 ing from the antennal and 

 mandibular somites respectively. Other writers, for instance, 

 Huxley, regarded it as marking the limits of the cephalic and 

 thoracic regions. There appears to be no ground, however, for 

 regarding this groove as of greater importance than some of the 

 other grooves of the carapace. In some cases an equally con- 

 spicuous transverse groove (e of Boas, " cervical groove " of Bouvier) 

 (Fig. 145, e, e) crosses the 

 carapace a little in front of the 

 cervical, and as this is the only 

 transverse groove, apparently, 

 to be found in any of the lower 

 Macrura (Stenopidea, Caridea), 



it seems at least as likely to 



e c I a 



afford an important morpho- Flo 146 



logical landmark. In SOme Carapace of CalUanassa novaebntanniae (Tlia- 

 r>ape nnrtirmo rvf tVia paranar-a lassinidea) from the left side. (After Borradaile. > 



cases portions tne carapace c , e> the gr ' ooves so lettered by Boas (see Fig 144) . 



may be separated by a longi- I.a,Zlneaonomptca(perhap8jdsotlieZi*wii*i- 



,. , , . J 3 . dim), the front part of which is the line & of 



tudinal groove Or Uncalcihed Boas; l.t, Unm thalassinwa (perhaps also the 



linp whirh mav PVPD form a z " ie ^ om "' ica ). * he front part of which is the line 



line, wni may ever >rm a ( ? O f Boas ; r, rostrum. 



movable hinge. Of this nature 



are the linea thalassinica (Fig. 146, l.t) of the Thalassinidea, with 



which the I. homolica of the Homolidae may perhaps be identical, 



and the 1. anomurica (l.a) of many Anomura, identified with the 



I. dromiidica of Dromiidae and the unfortunately named " epimeral 



suture" of other Brachyura. 



The sternal surface of the cephalothorax is very narrow in 

 many Macrura, but is often broad in those which have a depressed 

 form. It is broad in many Anomura and in all Brachyura, with 

 the exception of Raninidae. The thoracic sterna are usually clearly 

 distinguishable, and, in the lower forms, seem to preserve a certain- 



