!56 



THE CRUSTACEA 



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

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



jpicuous groove (Fig. 145, c) crosses 



Carapace of the Norway Lobster (Nephrops nor- 

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

 ring to the grooves of the carapace are those used by 

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

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

 of Bouvier, " posterior cervical groove " of Borradaile. 



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 

 ]\Iacrura (Stenopidea, Caridea), 

 it seems at least as likely to 

 afford an impoi'tant morpho- p^ i4g 



logical landmark. In some carapace of CaUianami nnvaehritanniae. (Tlia- 



pn«P« nr»rfinn« nf tTiP pnrqmrp lassinidea) from the left side. (After Borradaile.) 



Caseb poi HOns Ol une cai apdCt; ^^ g_ ^j^g gi-oo^eg >.o lettered by Boas (see Fig. 144); 



mav be separated bv a lonci- l.a,lineaan(:nnurica{per'ha.i>sa.\sothelineadromii- 



^. ■, , .J-.* 1 dioa), the front part of which is the line b of 



tudmal groove or imcalCined Boas; U, llnea thalassinim (perhaps also the 



1 • 1-1 i: linea homolim), the front part of which is the line' 



line, which may even form a ,? of Boas ; r, ro.strum. 



movable hinge. Of this nature 



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



which the I. homoUca of the Homolidae may perhaps l)e identical, 



and the I. anomurica (la) of many Anomura, identified with the 



/. 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 certairv 



