OF WESTERN SIND. 219 



median longitudinal line, and forms between the posterior pair of petals a well- 

 developed convex, hog-backed ridge. 



The peristome is very excentric in front, nearer the anterior than the lateral 

 margins of the test ; it is bilabiate, with the posterior lip broad, well arched, mode- 

 rately prominent and tumid, the anterior lip semicircular, and the neighbouring por- 

 tions of the test sloping inwards. 



The periproct is of moderate size, transversely oval, and placed at the summit of 

 the posterior extremity, the upper margin being slightly overhung by the test, and the 

 angle of truncation of the posterior extremity is slightly directed inwards, which gives 

 an overhanging character to the whole extremity ; beneath the periproct there is a 

 slight concavity in the test, which causes some tumidity to appear on either side of the 

 extremity near the margin. 



There are two well-developed fascioles on the test — one peripetalous, and the other 

 latero-subanal . The peripetalous fasciole is very sinuous ; it crosses the groove of the 

 odd anterior ambulacrum a short distance above the ambitus, traverses the anterior 

 interradia with a concave curve, bends sharply round the antero-lateral petals, and 

 after proceeding for a short distance beyond their extremity, is bent at right angles to 

 run parallel with the groove nearly up to the inner fourth of the petal ; it is then again 

 bent at right angles, and proceeds nearly parallel with the longitudinal axis of the test 

 until it curves sharply round the extremity of the postero-lateral petal, and passes far 

 up into the odd posterior interradium with a deeply reentering curve to cross the keel 

 and pursue a similar course on the other side of the test. The latero-subanal fasciole 

 joins the peripetalous fasciole at its sharp angular bend behind the extremity of the 

 antero-lateral petal, and proceeds thence in a direct course backwards and downwards 

 towards the posterior extremity, and passes beneath the periproct. 



The ornamentation on the abactinal surface is small, crowded, and comparatively 

 uniform, consisting of small primary tubercles with mamelons and disk-like scrobicules, 

 and with small, uniform, widely spaced, and irregularly disposed miliary granules in the 

 interspaces. On the actinal surface the primary tubercles are much larger and more 

 widely spaced, and the intervening miliary granules are more numerous and crowded. 



Bemarks.. This species has some resemblance to the Egyptian form Linthia 

 cavernosa described by de Loriol; but the Indian species is more widely expanded 

 laterally, and has much more deeply and definitely grooved ambulacra, and also 

 appears to be more tumid posteriorly. The forms are probably representative species. 

 Linthia orientalis has likewise some affinity with L. Tbergensis of de Loriol, from the 

 Nummulitic of Switzerland, but is distinguished by its more depressed test, by the 

 narrower petals placed in more sharply defined grooves, by the more excentric apex, 

 and by the difierent characters of the posterior extremity and marginal contour. 



As illustrative of the elasticity of form in this species, we have given drawings of 

 two remarkable monstrosities, in both of which an oblique development of parts has 

 taken place. The smaller of the two examples is also peculiar on account of its high 

 and conical abactinal surface, the longitudinal profile simulating in outline that of some 

 forms of Conoclypeus. 



