1878.] 319 [Weyenbergh. 



and present on their hind borders more pearls than in the male. 

 The sepia color of the whole body is generally a little darker, espe- 

 cially on the ventral face. 



My friend Prof. Dr. P. G. Lorentz sent me several specimens of 

 this species, found by him under stones in the Argentine province of 

 Entrerios, called generally "the Argentine Mesopotamia," on which 

 account I have given it this name. 



Pachylus Gouldii m. P. corpore prope triangularis colore nigro, 

 item prima tarsium articulatione, nee apicibus spinarum claris ; intra 

 oculos, non in ultimo segmento ceplialotlioracis spina ; femoribus paullo 

 curvalis et vix spinosis. Circulus clarus pedium articulationibus abest. 

 Tarsi P et 2 l paris ex 6, 3 li et If ex 7 articulis constantes. 



?. This species is a little larger and darker colored than the former, 

 its color being almost completely black. The form of the body is 

 more triangular, the abdominal segments being entirely withdrawn; 

 as this is not the case in the former species, it presents a more oval 

 form, approximating to a sphaaroid triangle. The palpi are a little 

 more armed, and their color and that of tl mandibles is black or 

 dark brown; the legs have the same color, only the tarsi are lighter, 

 although the large first joint is also black. The spines do not present 

 yellow points, and the legs generally are very warty. 



On each segment are observed more pearls than in the former spe- 

 cies, and they are placed in regular rows ; on the first polygonal false 

 segment two such rows are seen. Between the eyes is a spine, as in 

 the former species, but none occur on- the last segment of the cephalo- 

 thorax, while on the contrary the pearls on this segment are here a 

 little more elevated and sharper, the pearls on the back side of the 

 abdominal segments becoming little spines. 



The femora are not so curved in the form of an S, nor so stout, and 

 their spines are much weaker. The light rings around the articula- 

 tions of the legs are absent, only the first piece of the tibia presenting 

 still a trace of them. 



The thick border of the cephalothorax is regularly nacreous, and 

 this species more closely resembles in the general form of the body 

 P. acanthops Gerv. 



I possess only the female given to me by my friend Prof. Dr. B. A. 

 Gould, who captured it at Cordova.. 



I am now acquainted with various species of this family and of this 

 genus ; but this is the first time I have had in my hands animals of 

 this kind, enabling me to compare them with the fossil specimen that 



PROCEEDINGS B. S. N. H. — VOL. XIX. 21 MAY, 1878. 



