ACADEMY OF SCIENCES. 



71 



21. Mdhrax areolatus. nov. sp. 



The only species of Mithraclnce that have been, to my knowledge, previously 

 described from this coast are the Mithrax armttus of De Saussure, and the 

 Mithraculus coronatus of White and Stimpson. 



De Saussure's description is not accessible to me, and the only mention I 

 have of the species is in Stimpson's Crust, and Echi. Pac. Shores N. A., 

 where the reference is given, and the locality (Mazatlau) of the specimen in 

 the Mus. Phil. Acad. 



Mithraculus coronatus finds a place in the " Catalogue of Crustacea from the 

 Isthmus of Panama, collected by J. A. McNeil," by T. Hale Streets, but that 

 author does not state from which side of the Isthmus his specimens came. 

 I find the same species in S. I. Smith's " Brazilian Crustacea," from which I 

 infer that it is not unlikely McNeil's specimens were from Aspinwall. 



Dana says of Mithrax: " Articulus antennarum externorum Imus apice externo, 

 duabus spinis lovgis armatus," but the antennal spines in M. dichotomus of the 

 Mediterranean are very short, as they are in the present form. Mithraculus, 

 however, "is stated by Dana to be without long antennal spines. 



As the antennal spines in this species are evident, but are ' rather teeth or 

 lobes than spines, I assume that I have before me either De Saussure's Mith- 

 rax armatus or a new species — most probably the latter, more especially as, 

 besides the doubtful locality, the proportions of the carapax given by S. I. 

 Smith for his specimens of Mithraculus coronatus, do not agree with the present 

 species, which has the length and breadth more nearly equal. I subjoin a 

 short description : 



Carapax almost orbicular, slightly wider than long; front four-lobed, the 

 pre-orbital teeth projecting almost level with the two central lobes which con- 

 stitute the rostrum. Fixed joint of outer antennas with two obtuse teeth on 

 its outer apex. Antero-lateral margin with five teeth, including the post- 

 orbital, third tooth largest. 



Regions of carapax very distinct and subdivided into areolets answering to 

 those of the Xanthine and Chlorodinae; areolets with punctate surface, without 

 spines or teeth, and almost free from hair. Merus and carpus of first pair 

 with spiuose tubercles, hand smooth, cristate above. Those of female similar 

 but smaller. Posterior feet beset with spines on their exposed surfaces, and 

 denselv pilose. 



. M. M. M. M. 



Length of carapax 1G 13 



Breadth of ditto 18.5 15 



Localities — Port Escondido, San Jose Island, Gulf of California. Found at 

 low tide under stones and coral. Color, in spirits, light red. 



If this species should prove to be new, I propose to name it Mithrax areo- 

 latus. The females, when collected in the month of August, were loaded 

 with ova. 



No. 13. Male and female, in spirits. Gull of California. Fisher and Lock- 

 ington. 



