MUSEUM OF COMPAKATIVE ZOOLOGY. 117 



becoming spiniform toward the margins, which are armed with true spine9 

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

 width, and consisting of two rather slender, acute hoims. Basal joint of 

 the external antenna? 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 

 antennal 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, 0.73 ; breadth, 0.55 inch ; pro- 

 portion, 1 : 0.753. 



This species approaches SchizopTirys in the shape of its carapax, which 

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

 placed it ; but the rostrum is simply two-horned, and the orbits 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 16, 1869. Cast No. 12. 42 " 



Mithrax Holderi nov. sp. 



This species resembles M. 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 Tiarinia cornigera. There is a small spine on the hepatic region 

 and one at the lateral extremity of the branchial region. The anterior 

 spine of the basal joint of the antennas is nearly as long as the rostrum, 

 and there is another spine, very small, at the insertion of the movable 

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

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

 are spinulose and 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. J. B. Holder, who found it, also at the Tortugas, and I 

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

 the Museum of the Smithsonian Institution. 



Mithraculus sculptus Stm. 

 Maia sculpta Lamarck, Anim. sans Vert., V, 242. 

 Mithrax sculptus H. Milne-Edw t ards, Hist. Nat. des Crust., I, 322. Gibbes, 



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



de la Guadeloupe, p. 9. 

 Mithraculus sculptus Stimpson, Notes on N. American Crust., p. 58. 



