MUSEUM OF COMPARATIVE ZOOLOGY. 117 



becoming spiniform toward the margins, which arc armed with true spines 

 curving forward at their tips. Rostrum half as long as the interorbital 

 width, and consisting of two rather slender, acute horns. Basal joinl of 

 the external antennae armed with two spines, the anterior one of which is 

 slender, curved, and two thirds as long as the rostrum. The margin of 

 the orbit is armed with six spiniform teeth, not including those of the 

 antenna] joint. The feet are strongly spinose above, but the hands are 

 unarmed. The color in wet specimens, and probably in life, is a bright 

 deep red. 



Dimensions of a male : Length of carapax, o.7;j ; breadth, 0.55 inch ; pro- 

 portion, 1 : <».7o3. 



This species approaches Sckizophrys in the shape of it- carapax, which 

 is much more oblong than in other species of the genus in which I have 

 placed it: but the rostrum i- simply two-horned, and the orbit- are similar 

 to those of the typical forms of Mithrax. 



Off the Quicksands, January 23, 1869. Cast No. 1. 34 fathoms. 

 West of the Tortugas, January 16, 1869. Cast No. 8. 37 

 West of the Tortugas, January 10, 1869. Cast No. 12. 42 " 



Mithrax Holderi now sp. 



This species resembles .1/. acuticornis in the characters of the front, but 

 the carapax is broader and more strongly and closely tuberculated, the 

 tubercles occupying nearly the whole upper surface, causing it to resemble 

 that of Tinr'ini<i cornirjera. There i- a small spine on the hepatic region 

 and one at the lateral extremit.3 of the branchial region. The anterior 

 spine of the basal joint of the antenna 1 is nearly as long as the rostrum, 

 and there is another -p ne, very small, at the insertion of the movable 

 part nt' the antenna. The ambulatory feet are flattened above, giving the 

 joint- a somewhat trigonal form, and both margins of their upper surface 

 are spinulose ami ciliated. 



Dimensions of a male : Length of the carapax, 0.55 ; breadth. 0.48 inch; 

 proportion, 1 : 0.872. 



This species occurred at the Tortugas in 7 fathoms It is named in 

 compliment to Dr. .1. B. Holder, who found it, also at the Tortugas, and I 

 believe at low-watei mark, several years ago. Dr. Holder's specimen is in 

 the' Museum of the Smithsonian Institution. 



Mithraeulus sculpms Stm. 

 Maia sculpta Lam \i:< k, Anim. sans Vert, V, 242. 

 Mithrax sculptus II. Milne-Edwards, Ili-t. Nat des Crust., I, 322. Gibbes, 



Proc. Am. Assoc. Adv. Sci., 1850, p. 172. Desbonne et Schramm, Crust. 



i|e la Guadeloupe, p. 9. 

 Mithraeulus sculptus Stimfsox, Notes on N. American Crust., p. 58. 



