PROCEEDINGS OF THE NATIONAL MUSEUM. 



Superfamily HOMOLOIDEAE. 



Family HOMOLIDAE. 

 Genus HOMOLOPSIS (Carter, MS.) Bell. 



Homolopsis Bell, Mono. Foss. Malac. Crust. Gr. Britain, i)t. 2, 1862, p. 22. 



HOMOLOPSIS PUNCTATA, new species. 



Plate 33, fige. 1-3. 



Type-locality. — South Dakota: Eastern, Corson County; Pierre 

 Shale; Upper Cretaceous; July, 1915; W. H. Over; one specimen, 

 holotype, presented by the University of South Dakota, Vermilion, 

 South Dakota. 



Holotype.— Cat. No. 32058, U.S.N.M. 



Measurements. — Length of carapace of holotype, 19; width (esti- 

 mated), 25 mm. 



Description of holotype. — Carapace only, with a longitudinal break 

 on each side across the entire length. The posterior two-thirds is 

 fairly level except toward the side margins, but the anterior third 

 curves strongly downward. The grooves separating the gastric and 

 cardiac regions from the branchial region, and the epibranchial from 

 the mesobranchial lobe, and those limiting the hepatic region are 

 very deep. Much shallower grooves limit the mesogastric and uro- 

 gastric regions, and the mesobranchial lobe posteriorly. The surface 

 of the carapace is finely and uniformly punctate except on the elevated 

 portions, which are roughened with fine uneven granules, many of 

 which on the posterior part of the carapace are combined in short 

 transverse lines. The elevations form, in the main, regularly placed 

 bosses or areoles well separated ; four of these bosses are on the meso- 

 gastric region, two being median and two transverse and side by side 

 at the widest part; there is one boss on each epigastric lobe, and three 

 large and one small on each protogastric lobe ; two large and one small 

 boss on each epibranchial lobe. The cardiac region has one large flat 

 elevation, subtriangular, widest in front. The mass of granules on 

 the mesobranchial lobe is transversely obhque, followmg the shape 

 of the lobe. On the metabranchial lobes the granules are more scat- 

 tered and less elevated than elsewhere. 



The front between the eyes is equilaterally triangular, strongly 

 bent down, surface concave, tip apparently blunt. There are two 

 tubercles or spines (broken off) on the upper border of the orbit, 

 besides one at the outer angle. 



On the lateral margin there is a small spine not far from the orbit, 

 a large spine and two or three small ones on the hepatic region, and 

 two (one below the other) on the epibranchial lobe. 



Posterior margin bordered by a thin raised granulated rim. 



