or WESTERN SIND. 165 



is a strongly marked tumidity, amounting almost to carination, along the median line of 

 the posterior interradium, increasing towards the margin, and forming a prominent 

 swelling of the test beneath the level of the periproctal aperture. 



The ambulacral petals are narrow. The posterior pair are long, straight, and 

 lanceolate in form, expanding slightly towards the middle portion, and then contracting 

 towards their outer extremity. The poriferous zones are narrow, and vary only slightly 

 throughout their length ; the increase in breadth towards the widest part being slight, 

 and the contraction towards the extremity comparatively small. In the posterior 

 pair of petals the anterior zone is three or four pairs of pores longer than the 

 posterior zone. The breadth of one of the posterior petals is in the proportion of 

 about x^o°o o^ tb® length of the test ; and the breadth of the poriferous zone at its 

 widest part is one fourth of the width of the interporiferous area. The anterior 

 petals are much shorter than the posterior petals, the posterior zone is longer and 

 more curved than the anterior zone, the antero-lateral petals are rather narrower 

 than the postero- laterals, and the odd anterior petal is still narrower than the anterior 

 pair. The interporiferous areas are raised and tumid, which gives a very marked feature 

 to the species. The continuation of the poriferous zones beyond the petal is almost 

 indiscernible, there being no channel or depression to mark the course of the line of 

 small, single, and rather widely spaced pores. 



The ornamentation of the interporiferous areas is similar to that of the interradial 

 portions of the test. It consists of small, closely crowded primary tubercles, sunken in 

 narrow scrobicules, the intermediate portions being prominent, confluent, narrow, and 

 in all cases narrower than the width of the scrobicules. The ornamentation of the 

 actinal surface is somewhat larger than that of the abactinal, and maintains the same 

 general character. 



Unfortunately all our specimens are badly preserved in respect to their minute 

 structure, which has been more or less obliterated by weather action. The interradial 

 areas on the abactinal surface are very even, and present no tumidity or irregularities ; 

 and the same may also be said of their aspect on the actinal surface, excepting the odd 

 posterior interradium above noticed. 



The peristome is subcentral, and sunken in a slight depression of the actinal 

 surface ; around this depressed portion the test is tumid, and thence passes in a con- 

 tinuous and uninterrupted curve round the tumid margins and on to the abactinal 

 surface. In the large specimen the mouth-aperture and the neighbouring portions of 

 the test are concealed ; but in one of the smaller examples the peristome, which is 

 distinctly excentric in front, is conspicuously pentagonal, the sides very nearly equal, 

 and having the transverse diameter or breadth only a little greater than the longitudinal 

 diameter or length. The angles of the pentagon are rounded, and the surface of the 

 two anterior interradial spaces is faintly swollen, suggestive of incipient bourrelets. 

 The phyllodes are comparatively well developed, and four or five plates having supple- 

 mentary pores are present in a column. In this specimen there is a broad smooth band 

 devoid of primary tubercles extending between the peristome and the periproct. A 



