S. I. Smith oh new Crustacea from N. America. 119 



ated midway between the rostrum and the outer angle ; the 

 orbits entire, slightly removed from the anterior margin and 

 connected with it only by a suture. Antennas with the inner 

 margins approximate. 



This genus is most nearly allied to Ibacus and Parribacus 

 but is very distinct from both of them in the entire lateral mar- 

 gin of the carapax, the closing of the orbits in front, and the 

 form of the rostrum. 



Evibacus princeps, sp. nov. 



Whole upper surface verrucose and nearly naked ; five low, 

 tuberculose elevations on the median line of the carapax, of 

 which one is at the base of the rostrum, two on the gastric re- 

 gion, one on the anterior part of the cardiac, and one on the 

 posterior margin ; similar elevations on the middle of the sec- 

 ond and third segments of the abdomen, and a very slight one 

 on the fourth. Carapax strongly convex transversely ; the an- 

 terior margin nearly straight, except at the lateral angle where 

 it is slightly curved forward ; lateral margin strongly curved, 

 with a broad notch at the cervical suture behind which the 

 margin is very slightly, obtusely and irregularly toothed. An- 

 tennas together as broad as the anterior part of the carapax ; 

 the outer margins coarsely and irregularly serrate and their out- 

 line forming the segment of a circle. Everywhere beneath 

 naked and nearly smooth. External maxillipeds with the outer 

 margin of the merus divided into a number of slender proces- 

 ses. Legs so short that when bent forward in their natural 

 position they are concealed beneath the expansions of the car- 

 apax ; those of the first and second pairs with the superior 

 angle of the merus raised into an obtuse crest ; dactyli of all 

 the legs short and stout, in the female those of the posterior 

 pair closing against a process from the propodus. Abdomen 

 with the lateral projections of the second, third and fourth 

 segments long and rather acutely pointed, those of the fourth 

 shorter and triangular at tip ; lamella of the terminal segment 

 half as long as broad. Whole length of body, 14 in. ; length 

 of carapax, including rostrum, 5*8 ; breadth of carapax, 7'9. 



A single female specimen of this remarkable species, the first 

 of the Scyllaridae discovered upon the west coast of America, 

 was sent from La Paz, Lower California, by Capt. Jas. Pedersen. 



Arctus Americanus, sp. nov. 

 Carapax as broad as long, median crest high, covered with 

 low squamiform tubercles, tridentate, the anterior tooth small 

 and situated half way between the front and the second tooth ; 

 lateral crests very high, anterior portion with two teeth above 

 the eye and separated by a deep notch from the posterior por- 



