1903.J METAMORPHOSES OF DECAPOD CRUSTACEAXS. 27 



II. Orangon trispixosus Hailstone.* 



Length of the first larva 1-8 to 2-0 mm. ; average for twenty- 

 five spedmens being 1-9 mm. The body is light greenish yellow 

 in colour, with a conspicuous branching chromatophore placed 

 dorsally in the middle of the thorax. In general form the zojea 

 resembles that of C. nmms, the body being comparatively thick- 

 set and tapering gradually backwards. 



The lateral edges of the carapace are deeply arched below ana 

 perfectly smooth except for a blunt spine-like prominence below 

 the base of the second antenna (PI. YI. fig. 7). Anteriorly it is 

 prolonged into a short pointed rostrum barely half the lei^g^j^ ot 

 the peduncle of the first antenna. The carapace is not folded ott 

 over the eyes, so that the latter appear to be a part of it. Ihe 

 same pair of small outgrowths in front of the eyes as were 

 described in G. fasciatus also occur in C. trts2nnosits {m. Vi. 

 fio'. 8). No trace of them can be detected in later stages. 



'^The abdominal segments have their posterior dorsal edges 

 usually evenly rounded, without spines, but the fifth segment 

 sometimes has a pair of short dorso-lateral spines, and traces ot 

 them can often be detected. The tail-plate is of the usual form, 

 the spines being sharply pointed, and not blunt as in C. fasciatus 



(PL YI. fig. 8). 



In the form of the appendages C. trisjnnosus difi"ers so little 

 from G. oianics, which has been fully described by Sars, that it is 

 not necessary to describe them in full. The first antenna? ot 

 G. names, however, difi"er from those of G. trispinosus m that the 

 inner flagellum is armed with a few minute spines in addition to 

 the long cilia which are common to both (PI. YI. figs. 9 & 10). 

 The second antenna? in the two species agree in all respects, but 

 both species diff'er from G. echimolatus, which is in other respects 

 closely similar, in the much narrower form of the scale. 



In the later stages of the larva the body becomes more compact 

 and thick-set, having an appearance very characteristic of this 

 species and of G. nanus, from which, however, it is easily distin- 

 guishable by the absence of spines from the abdommal segments 

 and from the lower edges of the carapace. 



The rostrum is now very broad at the base, contracting suddenly 

 near its end and continuing as a short, sharp spine. As far as 

 the scanty material at my disposal for the study of the later stages 

 goes, the spines occasionally developed on the fifth abdominal 

 seo-ment of the first larva are lost with the first moult. 



"rhe gills appear in the fourth stage of development. At this 

 stage five gills can be seen placed, as it appears to me, m the 

 position of pleurobranchs— that is to say, they are well above 

 the apparent attachment of the legs (PI. YI. fig. 12). As the legs 



* Clans lias figured (1884, taf. vii.) a Cranqon larva which almost certainly belongs 

 to this species. The absence of abdominal spines, the form of the rostrum, aiid the 

 presence of an exopodite on the second pereiopod identify the larva with C. tn- 



