30 FAUNA OF BALUCHISTAN. 



The test is oval, imperceptibly truncated behind ; the upper surface is elevated, 

 " but somewhat flattened in the middle; anteriorly it falls perpendicularly, while on the 

 posterior side it slopes very slightly. The profile forms, therefore, a very charac- 

 teristic curve which cannot be mistaken. The sides are perpendicular, the ambitus 

 rounded, and the lower surface more or less convex. 



The apical disc is nearly central and very slightly elongated ; it is formed of 

 four genital plates which are perforated by large holes ; and of five small ocular 

 plates which are perforated by very minute holes ; the right antero-lateral genital 

 plate, which is larger than the others, serves as madrepore plate. 



The anteal sulcus is broad and flat iiear the summit, but quickly becomes 

 narrow and very deep towards the ambitus ; it is bordered by a rounded keel on each 

 side. 



The single ambulacrum, which is lodged in the anteal sulcus, is composed of 

 extremely narrow and fine poriferous zones ; the pores are small, obliquely arranged 

 in pairs, which closely follow each other in the upper part, but become more and 

 more distant towards the ambitus. 



The antero-lateral ambulacra are large, rather long and slightly curved forwards ; 

 they are composed of two very unequal poriferous zones ; the anterior one is 

 extremely narrow towards the summit, but becomes a little wider at its lower end ; 

 the pores are very small, and arranged in horizontal pairs. The posterior zone is a 

 little flexuous and very broad ; the pores are of very unequal size ; those of the 

 inner row are small and round, those of the outer row elongated, and joined to the 

 former ones by a long but narrow furrow. Each pair of pores is separated by a 

 long but narrow ridge covered with one line of minute granules, which are 

 easily worn away. Their basal portions are very indistinct and are only marked 

 by a few pores each situated on a tubercle near the anterior comer of the mouth. 



The postero -lateral ambulacra show the same arrangement of the poriferous 

 zones, but they are a little shorter and less broad, while on the other hand they are 

 somewhat more flexuous. Their basal portions are marked by two rather broad, 

 apparently smooth, bands, which extend on either side of the plastron from the 

 posterior border to the mouth. A few scattered pores are very distinctly seen near 

 the corners of the mouth ; they are more crowded and situated on a tubercle, which 

 is surrounded by a deep scrobicule. 



The peristome is situated near the anterior border in a depression formed by 

 the deep grooving of the anteal sulcus ; it is rather small, semilunar in shape, and 

 possesses a strong upper lip. 



The periproct is oval, rounded above, but pointed below, with its longest dia- 

 meter in perpendicular direction ; it is situated at the upper end of a groove which 

 deeply indents the posterior border. 



The tubercles are numerous and of two kinds ; the whole of the upper surface 

 except the two edges of the anteal sulcus is covered with homogeneous fine granules • 

 on the base and on the edges of the anteal sulcus the tubercles are considerably 

 larger and surrounded by a scrobicule which is particularly well marked, like those on 

 the edges of the anteal sulcus ; very fine granules are densely distributed between the 



