6 W. T. OATiMAN. 



A difference which may possibly he of greater importance than any of tliose 

 mentioned aliove exists, as Prof. Coutiere has pointed out, in the branchial system. 

 In addition to the five pleurobranchise possessed l)y C. antarcticus, C. franciscorum 

 has on each side a well-developed arthrob ranch ia at the base of the third maxilliped. 

 The statements made by various writers as to the gill-formula of the common shrimp, 

 and of the genus of which it is the type, are curiously conflicting. Although 

 Huxley, in 1878, Boas, in 1880, and Claus, in 1886, gave the number of gills in 

 C. vulgaris correctly as six, more recent authors seem to have overlooked the 

 arthrobrauchia of the third maxilliped, which, although small, is not at all difficult 

 to see. Sars, in 1890,* gives among the characters distinguishing Crangon from 

 PontopMlus, the presence of five gills in the former and six in the latter genus, 

 and this statement is copied by Mr. Stebbing.f Ortmann, in his revision of the 

 Craiir/onidse in 1895, J names a numlier of species of Cranr/on which he has examined 

 ■ and found to have only five gills. One of the names mentioned, " typicus," 

 does not appear elsewhere in the paper, but it may be conjectured that it refers 

 to the typical form of the species C. vulgaris. Two other species on the list are 

 C. affiiiis and C. franciscorum. In these three species, and also in C. allmanni and 

 C. nigricauda, I find, on the contrary, that the arthrobrauchia is well developed. In 

 the absence of trustworthy data as to the occurrence of this gill in the other species 

 from the northern hemisphere, it is not possilile to estimate the importance to be 

 attached to its absence in C. nntarcticus. It may y)e noted, however, that it is absent 

 in the characteristically Arctic genus (or subgenus) Sclerocntngnn, v/hich is otherwise 

 not very sharply defined from Crangon, and to which, in its strongly sculptured 

 carapace, the present species has some resemblance. Prof C'outiere, in his preliminary 

 notes on the Decapoda of the ' Belgica,' has called attention to this resemblance to 

 Sclerocrangon ; but he suggests, with some hesitation, the establishment of a new 

 subgenus, Nottid'angaa, for the Antarctic species. I have not been able to examine 

 the structure of the male pleopods, to which he attaches some importance, but the 

 other characters which he mentions do not seem to me to justify this step. 



Larvce. — A numlier of larvje of this species were collected, all in a stage of 

 development corresponding to the " last larval stage " of Prof. Sars. The rostrum is 

 very long and slender, extending well beyond the eyes. There is a small median dorsal 

 tooth on the carapace, about midway between the back of the orbit and the "cervical " 

 groove, and a little in front of it is a rounded papilla (represented in some of Sars's 

 figures) probably representing the problematical " dorsal organ " of some Euphausid 

 larvse. The abdomen is unarmed, except for the paired spines at the posterior end of 

 the fifth somite, which are long and slender, almost as in Sars's figures of the larva) of 

 Pontophilus, and, as in that genus also, the sixth somite is very long. The telson is 

 very large, in the form of an almost equilateral triangle, with the posterior margin 



♦ Avph. Math. Naturvid, xiv. (1H90). p. l,->;!. f Hist. Crustacea (189;l), p, 227, % rroc, Acad. Nat. Sci.. 



Philad. (1895), p. 175, 



