Notes on North American Crustacea. 177 



our possession upon the Brachyiira and Anomnra ; but our 

 knowledge of the devehipment of these two sub-orders upon 

 this continent lias been so greatly increased by recent investi- 

 gations, that it is found necessary to review them in this second 

 part, in order to include the results. As will be seen below, 

 these rich materials have been chiefly accumulated by Mr. 

 John Xantus, in the course of his most successful researches 

 into the fauna of Cape St. Lucas, at the southern extremity of 

 the peninsula of Lower California. We have also added a 

 number of interesting species collected in the West Lidies by 

 Mr. A. H. Riise of St. Thomas. 



The type-specimens of all the species herein described are in 

 the Museum of the Smithsonian Institution. 



MAIOIDEA. 

 Pelia mutica. 



Pisa mutica Gibbes; Proc. Am. Assoc. 1850, p. 171. 



This species belongs to Pelia of Bell, an American genus, 

 species of which are found on both sides of the continent. It 

 differs widely from Pisa in the want of a prseorbital spine, in 

 the long narrow basal joint of the external antennse seen from 

 above along the side of the rostrum, and in the compressed feet 

 with unarmed terminal joints. 



It was found in Charleston Llarbor by Prof. Gibbes and 

 myself. It has also occurred to me in Beaufort Harbor, N. C, 

 and in Holmes' Hole, Martha's Yineyard. It most commonly 

 occurs among ascidians on the piles of wharves, below low tide 

 mark. 



Thoe sulcata, nov. sp. 



Allied to T. erosa Bell, Trans. Zool. Soc. of London, ii. 48, 

 pi. ix. f. 4, — a Gallapagos species. But the carapax is generally 

 more triangular, with the sides and subhepatic regions granu- 

 lated. Rostrum less deeply bifid. Frontal region with two 



