48 BULLETIN 138, UNITED STATES NATIONAL MUSEUM 



ZANTHOPSIS VULGARIS, new species 



Plates 13 and 14 



Description. — Outlines of carapace: Carapace very much arched 

 from front to back, less so from side to side. Anterior and antero- 

 lateral margins form almost a semicircle (pi. 13, fig. 1) ; antero- 

 lateral margins very thick, cut into four lobes, the one nearest the 

 orbit broad and shallow, the others increasing in prominence to 

 the lobe at the lateral angle which is about midway of the length 

 of the carapace. Postero-lateral margins moderately convergent, 

 slightly convex. Front between a fourth and a fifth as Avide as the 

 carapace, with a triangular median sinus forming two oblique lobes, 

 each composed of two teeth or lobes separated by a broad shallow 

 sinus; the submedian teeth are rounded and larger than tlie outer 

 teeth, which tend toward acuteness (pi. 13, fig. 2). 



Areolation of carapace : The deepest furrows on the dorsal surface 

 of the carapace consist of two crescentic, impressed lines separating 

 the branchial from the metagastric-urogastric-cardiac regions. The 

 postero-lateral borders of the cardiac region are marked by a 

 wrinkled fold in a broad depression. The largest areolo of the 

 carapace occupies the posterior part (about half) of the branchial 

 region and is subcircular and nearly as high, in many instances 

 quite as high, as the cardiac region. ^'^ The metagastric region, which 

 is not separated from the narrow mesogastric region, lies at the 

 highest part of the carapace; either side of it there is a small round 

 branchial areole less high. Between this and the large areole and 

 the crescentic groove there is a narrow, low, curved areole pointed 

 behind. On the epibranchial region there is an oblong, elongate 

 areole, obliquely tranversely placed, separated In^ the broad cervical 

 suture from the postero-external angle of the protogastric region, 

 and from the lateral marginal lobe by an equally deep furrow ; this 

 elongate lobe is a distinguishing feature of the species. The greater 

 pai't of the hepatic region is occupied by a single elevation separated 

 from the marginal lobes. The gastric subdivisions are separated by 

 shallow furrows ; the mesogastric region has an acuminate point from 

 which a groove is continued to the frontal border. In specimens 

 which have the outer layer of shell preserved, the areoles are shown 

 to be abundantly but not closely covered with unequal granules, the 

 interspaces are smooth. The coarsest granulation is on the postero- 

 lateral portions of the carapace. 



Orbits, antennae, and maxillipeds: The orbit is broad-oval, its 

 greatest length is about equal to half the width of the front. Edge 



^"The branchial lobes are often considerably swollen (pi. 14), having the appearance 

 of being infested by a parasite. As the swellings are in each case equally developed on 

 both sides of the carapace, tlieir presence is more likely due to adaptation to an arid 

 condition existing at the time of their destruction. 



