OF WESTERN SIND. 83 



The antero-lateral ambulacra are long, on rather deep grooves, faintly flexuous, 

 rounded, and nearly closed where the fasciole bounds them, and narrow apically. The 

 anterior poriferous zone is on the flank of the groove, the narrow or interporiferous 

 zone is on the floor, and the posterior poriferous zone on the other flank, and, like its 

 fellow, is steeper near the apical system than in the outer third. The pairs of pores 

 are separated by granular costee ; and there are from 20 to 23 pairs of pores. The angle 

 formed by the diverging ambulacra is about 110°-115°. 



The posterior lateral ambulacra are small, petaloid, close, separated by a narrow 

 keel, rather deep, nearly closed, rounded where in contact with the fasciole, and the 

 outer poriferous series is more curved than the inner. There are from 14 to 16 pairs of 

 pores. Their grooves are comparatively shallow. 



The interradial areas are narrowed at the apex, and form moderately elevated, 

 narrow, rounded keels, ornamented with a few distant tubercles. On the flanks the 

 plates have a slight bulge ; and thus a series of longitudinal elevations is formed, 

 rendering the test slightly gibbose. 



The ornamentation is largest in the anterior interradium, and especially on the 

 margins, and it becomes larger and sparer near the peristome. It is smaller in the 

 lateral interradia, behind a narrow line of minute granulations resembling a fasciole, 

 which passes along the surface of the extrapetaloid part of the antero-lateral 

 ambulacra. The ornamentation consists of low rounded tubercles or faintly rounded 

 scrobicules. The surface around the peristome is free from ornamentation; and the 

 plastron has a lai'ge ornamentation in regular oblique rows, which diminishes towards 

 the posterior point. 



The peristome is broader than long, is narrow from behind forwards, rounded at 

 the outer angles, and is on the whole slightly curved and crescentic. The posterior lip 

 is on a lower level than the anterior edge ; the whole edge has a rounded-off rim. The 

 ambulacral pores are scanty in number. 



The periproct is oval, longitudinal, high up, and is in the posterior truncation, 

 which is slightly hollowed out and bounded by faint ridges which enclose an oval 

 space and pass over the margin to unite at the point of the plastron. 



The peripetalous fasciole is in relation with the gibbous swelling of the plates along 

 its course. It is broad at the rounded ends of the antero-lateral petals, and passes for- 

 wards and inwards as a narrower band to a gibbosity on the keel of the odd ambulacrum, 

 over which it passes with a bend, the convexity forwards, not far from the margin. 

 Behind, the fasciole passes along the edge of the end of the antero-lateral ambulacra 

 backwards and inwards to a gibbosity, and then enters the angle, passing close to the 

 commencement of the narrow keel of the lateral interradium. Thence it reaches the 

 anterior edge of the posterior petal, which it bounds ; turning round the termination 

 of the petal, it crosses directly over the narrow posterior keel to the other side, and 

 pursues a corresponding course. The fasciole is broadest close to the outer part of the 

 antero-lateral ambulacra, and is narrow elsewhere. 



The lateral fasciole is very narrow ; it starts from the gibbosity behind the outer 



