48 T. 8. Hall: 



Peristome large, triangular, and showing the curious obliquity 

 of the genus. Periproct large, long, oval, pointed at the posterior 

 end. 



Tubercles sunken, crowded, imperforate. There do not seem 

 to be any of the generically characteristic tubercles of epistoma, 

 the spaces between the tubercles being smooth. This, however, 

 may possibly be due to weathering. 



Mkasurements. 

 Length, 21. Breadth, 14. Height 7. 



The genus has not been previously recorded from our older 

 tertiary. It ranges from the Miocene in the West Indies, and 

 there are two very widely-spread recent species. 



Locality. — "' Filter Quarries," Batesford, one specimen some- 

 w^hat obliquely crushed, and a fragment. Barwonian (? Eocene). 



Prenastep aldingensis, n. sp. 



Test small, oval, tumid, posteriorly truncated, flattened actinally, 

 Apical system small, excentric in front. Peristome transverse, 

 slightly crescentic in front (damaged posteriorly). Ambulacra 

 in extremely faint depressions near the apical system, the 

 depressions only noticeable in oblique light. At about two 

 mm. from the apex the ambulacra have become flush. Pores 

 minute, round, the pairs about their own width apart. Ambul- 

 acra narrow, straight, open. Towards the ambitus the pores of 

 the odd ambulacrum are elongate slits, very far apart. Actinally, 

 round the peristome the pores are also slit-like. 



Periproct high on the posterior truncation ; as far as can be 

 seen, it is large and pointed at its uper end. 



Primary tubercles very small, perforate, crenulate, scrobiculate. 

 They are sparsely scattered over the dorsal surface. There are 

 four rather large ones at the apex, which are apparently close 

 to the outer sides of the basal pores. The tubercles are larger 

 dorsally on the anterior ambulacra, and also actinally, near the 

 ambitus. The sternum is hidden by matrix. There is a faint 

 ridge bounding the scrobicular areas, which are not sunken. 

 Actinally the tubercles are excentric anteriorly on the scrobi- 

 cular areas. Outside the scrobicules is in most cases a single 

 row of miliaries forming a ring, and a few scattered miliarias 

 occur as well. 



