18 Mr. H. Seeley on Cambridge Palaeontology : — 



except towards the base, where a few others are introduced. 

 From theai descend short transverse ridges, forming pits, in 

 which the pores are placed. The pairs of pores are in single 

 file throughout. The interambulacra are furnished with two 

 rows of tubercles of four each ; the uppermost of the left row 

 is very large. The bosses are hemispherical and crenulated. 

 The scrobicuhe are surrounded by a row of granules. The 

 peristome is rather pentagonal. 

 Lat. -£$ inch, alt. ■£■% inch ; oral opening ^ inch ; apical disk 



** inch - 



This form is easily distinguished by the characters of the 

 apical disk, the narrower ambulacral areas, larger interambulacral 

 tubercles, small size, &c. 



It is one of the many unique treasures contained in the 

 cabinet of my friend Mr. Carter. 



A single specimen has been found in which the following cha- 

 racters may be generic : — 



Poles opposite. Apical opening moderate [cordate] . Oral open- 

 ing entire, circular. Tubercles imperforate, crenulated. The 

 ambulacral areas are half the width of the interambulacra. 

 In them large tubercles are developed on one row of plates, 

 and small tubercles on the other ; in the interambulacral 

 areas are two primary rows. Pores bigeminal. The pori- 

 ferous zones are wide, and much impressed above. 



Should the characters presumed to be generic prove constant, 

 the name Caseolus might perhaps be used to indicate them. 



[^Cyphosoma] impressa. 



Pentagonal, greatly depressed, flattened above, concave below. 

 Oral opening deeply sunk, circular. Apical aperture heart- 

 shaped, extending into the odd interambulacrum. Ambulacra 

 narrow, furnished with one row of about seven tubercles, 

 which are as large as those of the interambulacra. On the 

 other series of plates is a row of small granules, about three 

 or four to each large plate : near the apex two or three small 

 tubercles are developed. The poriferous zones are impressed 

 on the upper part. The pores are placed in a straight line 

 between elevated transverse ridges. There are two primary 

 rows, and two secondary rows between these. In the inter- 

 ambulacra are two rows of tubercles of seven or eight each. 

 Areola? large, radiated, scarcely impressed, nearly circular, 

 and margined by a row of granules, which separates them 



