596 THE LARV.l^ OF CERTAIN BRITISH CRANGONID^. 



the length of the rostrum ; the average of twenty-five specimens 

 being 1'9 mm. The body is somewhat transparent and of a light 

 greenish yellow colour, with a conspicuous, large chromatophore 

 dorsally in the middle of the thorax. In general form it resembles 

 closely the zosea of Cheraphihis nanus, the thorax being not con- 

 spicuously broader than the first segments of the abdomen, which 

 tapers gradually backwards. 



The rostrum is short and pointed, but in later stages it is Ijroad 

 at its base and contracted sharply towards the apex, as is the case 

 also in C. nanus. The ventral edge of the carapace is smooth though 

 ending in front in a single short spinous prolongation. The abdominal 

 segments are usually quite smooth, but the fifth segment may in some 

 cases have a pair of short lateral spines. The tail plate is of the usual 

 Crangonid type, with seven strong ciliated setae on either side. 



The inner flagellum of the first antenna is closely ciliated as in 

 C. eclvinulatns. In C. nanus there are a few minute spines in addition 

 to the cilia. The scale of the second antenna is narrow and elongated, 

 with seven internal setcC and two setae and a small spine apically. 

 Externally there are two small setae. The second antenna agrees 

 closely with that of C. nanus, but differs from that of C. cchinulutus 

 in the narrowness of the scale. 



The remaining appendages show no very characteristic features. 

 The larva of C. trispinosus may be distinguished by its small size, 

 and by the absence of teeth on the lower edge of the carapace and 

 of spines on the third and fourth abdominal segments. 



The Larva of .ffigeon fasciatus (Kisso). 



The length of the larva when just hatched varies from 1"8 to 

 2'05 mm., the average being 2"0 mm. for twenty-four specimens. This 

 measurement is exclusive of the rostrum, which is about "17 mm. 

 long at this stage. In general form of body the zoaea is not unlike 

 that of C. trispinosus, but it is easily distinguishable. The thorax 

 is not much broader than the first abdominal segment, and the 

 carapace is prolonged forward into a long pointed rostrum. In 

 later stages the rostrum is broad at the base and sharply contracted 

 distally. The lower edge of the carapace is arched and without teeth, 

 ending in front in a small blunt process. 



The abdomen tapers but little, though the characteristically ex- 

 panded epimera of the second segment make it appear considerably 

 broader than the others. The third segment has a pair of backwardly 

 directed dorsal spines ; the fourth a pair of small knobs on the 

 posterior dorsal edge, while the fifth segment has on either side a 



