288 Major A. Alcock and Capt. A. R. S. Anderson on 



On the hands and ringers of the third and fourth pairs are 

 small corneous prickles, arranged either singly or in trans- 

 verse rows of two or three. 



The abdominal segments are dorsally carinate, the carina 

 being most prominent on the anterior three segments, 

 gradually widening and becoming less and less marked on 

 the fourth, fifth, and sixth segments. 



The telson ends in a rounded central lobe, running down 

 to which is a dorsal central groove. On the lateral margins 

 of the telson are a few small teeth and near the proximal end 

 one considerably larger than the others. 



A median longitudinal ridge divides the inner plate of the 

 swimmeret into two nearly equal parts and terminates distally 

 in a small sharp tooth. A similar ridge divides the outer 

 plate of the swimmeret into two subequal parts ; the movable 

 segment is very small, its inner end just passing beyond the 

 central ridge, and the margin of the suture is armed with 

 a few small acute teeth, as also is the distal half of the outer 

 border of the plate with five similar small teeth. 



In Calastacus investigatoris saidfelix both male and female 

 external genital orifices are present, as in Parastacus, 

 described by Dr. Emar Lonnberg in ' Zool. Anzeiger ' of 

 June 2, 1898. On this point Faxon is silent in his descrip- 

 tion of Calastacus stilirostris. 



CALLIANASSA, Leach, A. Milne-Edwards. 

 Callianassa h'gnicola, sp. n. 



This is a small species, the carapace measuring 3*3 millim., 

 the abdomen 11*5 millim. 



The form of the carapace resembles that of Callianassa 

 pachydactyla, similar longitudinal and oblique grooves being 

 present in both species. Anteriorly it is produced into an 

 acute small rostrum. 



The abdominal segments are all smooth. The first is 

 considerably narrower in front than behind ; the second, 

 which also increases in width posteriorly, is by far the longest 

 of all the segments and almost twice the length of the first. 

 The telson is well developed, diminishing in width poste- 

 riorly, and on its dorsal surface is a broad median furrow 

 expanding posteriorly to the full width of the telson ; the end 

 is square, with the corners rounded off. The outer plate of 

 the swimmeret is about ^ longer than the inner plate and 

 armed on its outer straight margin with a small tooth. The 

 pleurae of all the abdominal segments are very short, smooth, 

 and gently rounded at their margins. 



