84 FAUNA OE BALUCHISTAN. 



Hemipneustes comprbssus, spec. nov. PL VII. fig. 3-3o, 4, PI. VIII. fig. 1-la, 



2-2b. 



Dimensions of three specimens. 

 Length L =66 54 49 



Breadth b =60 50 45 



Height h . =38 32 29 



4 =-91 -92 -91 



L 



Ji =-57 -59 -59 



L 



The test is suborbicular, there being little difference between breadth and 

 length ; the upper surface is elevated, but flattened in the middle ; at either end as 

 well as at the sides it falls off vertically, lower surface nearly flat or only slightly 

 convex on the plastron. The test has therefore a vertically compressed appearance 

 and the profile line in either direction resembles a rectangle with rounded corners. 

 Ambitus rounded. 



Apical disc nearly central, slightly advanced, and only slightly elongated ; it is 

 formed of four genital plates of nearly the same size, perforated by large round 

 holes, and five smaller ocular plates which are perforated by minute holes ; madre- 

 pore plate slightly larger than the other genital plates. 



The anteal sulcus is hardly perceptible on the upper surface, where it is indica- 

 ted by a shallow depression only, bordered by two lines of strong tubercles', but it 

 rapidly deepens on the anterior side, while it becomes rather narrow towards the 

 mouth. Ambulacra exactly like those of H.. pyrenaious, but apparently the postero- 

 lateral ambulacra meet at a less acute angle than with S. pyrenaious. 



Peristome and anal opening like those of E. pyrenaious, but, owing to the more 

 depressed shape of the test, the anal opening is perceptibly nearer to the posterior 



border. 



Tubercles exactly the same as those of JS. pyrenaious ; on the lower surface the 

 tubercles in the centre of the plastron are apparently finer than in E. pyrenaious ; 

 basal portion of the postero-lateral ambulacra covered with fine, minute granules. 



LooalHy and stratigraphioal pos2^*ow.— Together with Hemipneustes pyrenai- 

 ous, but apparently rarer than that species in horizon Nos. 2 and 4, Dds valley 

 and No. 8, Mazdr Drik. 



Bemarks. — I hesitated for a long time in separating this species from E. pyre- 

 naious, because it seemed to me only a variety of this form : but having a consider- 

 able number of specimens under examination, which all exhibited the same charac- 

 ters, I think I am justified in describing them under a new name. The chief 

 feature, if not the only difference between the two species, rests in the different 

 shape of the test ; for while E. pyrenaious has a pronounced elliptical shape, E. oom. 

 pressus is nearly orbicular, the greatest breadth being almost the same as the great- 

 est length. E. oompresms in this respect follows closely E. Zeymeriei ; on the 

 other hand the vertically compressed shape of the test distinguishes E. Gompressua 

 easily from the more inflated E. pyrenaious ; in fact as regards this feature E. com- 

 presses is the lowest known species of this genus and contrasts strangely with such 

 forms as M. africanus or E. radiatus. 



