igio. 1 S. Kemp : Notes on Decapoda. 175 



lacinia is slightly broader at the apex than at the base and is a 

 little narrower than the adjacent lobe of the external lacinia. The 

 apex of the endopod is narrow and bears from three to five spines 

 on its external aspect. 



In the first maxillipede the third joint of the endopod is oval 

 and very nearly twice the length of the second; the basal joint 

 bears five stiff spines on its inner distal margin. 



The carpus of the first pair of peraeopods is shorter than . 

 the chela and is only a little more than half the length of the 

 merus. In the second pair the chela is seven-eighths the length 

 of the carpus and the dactylus is equal to, or shorter than, 

 the palm. In the third pair the merus and carpus are of the 

 same length; the chela is half, or a little more than half, the 

 length of the carpus and the dactylus is a trifle shorter than the 

 palm. 



The sixth abdominal somite alone is dorsall}' carinate and all 

 the median tubercles on the abdominal sterna with the exception 

 of the first are blunt and inconspicuous. The apex of the telson 

 is truncate and bears four or five pairs of plumose setae, of 

 which the middle pair is the longest, between the stout marginal 

 spines. 



The petasma (figs. 5, 6) bears some resemblance to that of Gcn- 

 nadas parvus, but, judging by the dissimilarity which exists in re- 

 gard to the other characters, more especially in the antennal scale 

 and antennular peduncle, it does not seem likely that the two 

 forms are allied to one another in any really close manner. The 

 outstanding lobe on the anterior aspect varies considerably in 

 shape ; it is sometimes pointed apically and reaches as far as the 

 distal margin. 



I have associated this species with the name of Ivieut.-Colonel 

 Alcock who has given a very accurate description of the thelj^cum 

 {loc. cit., 1901, p. 47, suh '' G. parvus"). His account, which 

 ma}^ be compared with fig. 8, runs as follows : — "The thelycum 

 consists of a horizontal, subtriangular plate or tubercle, placed 

 between the third pair of legs, followed by two transverse bars 

 between the fourth and fifth pairs. The first of these bars is 

 somewhat W-shaped with the posterior notch of the W filled 

 by a tooth in the middle of the anterior border of the second 

 bar." 



The specimen which Miss Rathbun ' has attributed to Gen- 

 nadas parvus, remarking that the thelycum agrees exactly with 

 Alcock's description, is certainl}?^ quite distinct from the species 

 here described. The true female of Spence Bate's G. parvus, 

 which I have recently discovered in a collection made by Dr. J. 

 Stanley Gardiner, is, in respect of the thelycum, wholh* different 

 both from the present species and from that figured by INIiss 

 Rathbun. 



1 Rathbun, Bull. U. S. Fish Comm. for 1903, 1906, p. 907. 



