54 J. R. KiNAHAN on the Britannic Species of 



ANALYSIS OF DIAGNOSTIC CHAEAOTEKS. 



Firstly, the Rostrum. Of this two marked forms exist : — 



I. In Crangon fasciatus; C. sculptus; C. carinicauda {fide descript.) ; 

 C. cataphractus {fide specimen in Brit. Mus. collection, presented 

 by RI. Spinola) ; its apex is truncate ; the anterior angles more 

 or less acutely produced, so as to become somewhat bifid 

 (^geon). — Plate I., Figs, iv., v., vi. 

 II. In the other species enumerated it is somewhat shortened, always 

 triangular, and acute or rounded at apex (Crangon and Chera- 

 philus). — Plate I., Figs, i.-iii. 



Secondly, the Carapace: — 



I. In all the species included under the first section named above 

 (-^geon), there are rows of spiny teeth, or knobs, on the gastric 

 regions both lateral and median, and also on the branchial. 

 In the species having a simple beak we find two arrangements. 

 II. In Cr. trispinosus, Cr. bispinosus, Cr. intermedius {fide descript), 

 Cr. bidentatus {fide descript.), Cr. angusticauda {fide descript.), 

 Cr. Pattersonii, Cr. spinosus, Cr. boreas {fide spec, in Brit. Mus.), 

 Cr. munitus {fide descript.), there are rows of carinations — gene- 

 rally three on each branchial, and one to three on the gastric 

 regions, — the carince being sometimes represented by spiny teeth ; 

 at others, simply by knobs, but always appreciable: these are 

 stronger in the adult than in the younger specimens. Here also, 

 probably, come in Cr. capensis and Cr. nanus, which are described 

 as having the carapace keeled (Cheraphilus). 

 III. In Cr. Allmani, Cr. affinis {fide descript.), Cr. nigricauda {fide de- 

 script.), Cr. propinquus {fide descript.), Cr. rubropunctatus {fide 

 descript.), Cr. Franciscorum (_/jf/e descript.), and Cr. vulgaris, the 

 carapace is totally destitute of carin£E, its greatest armature being 

 three spiny teeth, viz., one on the median gastric, and one 



