PETROLISTHES AGA8SIZII. 69 



Station 3413. 1360 fathoms. 2 niale.s, 6 fern. 

 " 3429. 919 " 2 males. 



3431. 995 " 1 male, 2 fem. 



3432. 1421 " 1 male, 1 fem. 



The carcinoecia are Ga.stropod shells whicli support, and in most cases 

 are more or less completely absorbed by, a sea-anemone or a colony of 

 EpizoantJms. Among the determinable shells are Solanella, Nutica, and Plm. 



Family PORCELLANID^. 



PETROLISTHES Stimp.s. 

 Proc. Acad. Nat. Sci. i'liila., X. 227, 1858. 



Petrolisthes occidentalis Stimps. 



Ann. Lye. Nat. Hist. N. Y., A^II. 73, 1859. 



Reef at Panama, March 12. 4 males, 8 fem. ovig. 



In recent alcoholic specimens the transverse ridges and squamiform tuber- 

 cles of the carapace are dark red, the intervening spaces yellowLsh. The 

 lower surface, including the abdomen, deep madder. 



Petrolisthes agassizii Fax. 

 Plate XV., Firj. 1, T\ 



Bull. Mus. Coinp. Zoiil., XXIV. 174, 189.3. 



In this pretty species the whole upper surface of the carapace is crossed 

 by piliferous plications or rugaj which are broken and irregular on the ante- 

 rior half of the carapace, but posteriorly they extend acro.ss the whole upper 

 surHice without a break. The length of the carapace is equal to the breadth, 

 the front is prominent, somewhat deflexed, not trifid ; a longitudinal median 

 sulcus extends back some distance on the gastric region. The supraorbital 

 margin is convex and thickened, separated from the front by a deep groove ; 

 the posterior angle of the orbit is obtuse, but denticulated. On the lateral 

 margin of the carapace a minute spine is discernible just behind the cervical 

 groove. The pterygostomian region is clothed with a dense pubescence. 

 The basal joint of the antenna has a ])rominent denticulated lobe on its inner 

 side. Chelipeds : merus rugose, armed with a strong tooth on the distal 

 internal angle ; carpus long, thickly set with flat, squamous tubercles both 

 above and below, anterior border three-toothed, upper surface with two Ion- 



