'II 



ACADEMY OF SCIENCES. 9 



21. Mdlirax areolatus. nov. sp. 



The t)uly species of Mithracinoi that have been, to my knowledge, previoiisly 

 described from this coast are the Mithrax urmitus 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 Mils. 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 si^ecies in S. I. Smith's " Bi'aziliau Crustacea," from w^hich I 

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



Dana says of Mithrax: '' Articulus antennarum externorum Imus apice externa, 

 diiabus spinis longis armatus," but the autennal 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 sjDecimens of Mithraculus coronatus, do not agree with the present 

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

 short description : 



Carajjax 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 antenna with two obtuse teeth on 

 its outer apex. Autero-lateral margin with live teeth, including the post- 

 orbital, third tooth largest. 



Regions of carapax very distinct and subdivided into areolets answering to 

 those of the Xanthiuse and Chlorodinse; areolets with punctate surface, without 

 si^ines or teeth, and almost free from hair. Merus and carpus of first pair 

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

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

 densely pilose. 



& -P 



M. M. M. M. 



Length of carapax 16 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 sj^irits. Gulf of California. Fisher and Lock- 

 ington. 



