NO. 3 CASSIDULOID ECHINOIDS — KIER I7I 



genus probably do belong to Nucleopygus, one of them. Forbes' 

 Nucleolites morrisii, definitely does not. Unfortunately, this species 

 had never been well figured, and the characters that distinguish it 

 from Nucleopygus were not known to Lambert and Thiery, IMorten- 

 sen, or Pomel. 



Range and distribution. — Lower Cretaceous (x\lbian-Cenomanian), 

 England. 



OCHETES MORRISII (Forbes) 



Plate 25, figures 5-7; text figures 144-146 



Nucleolites morrisii Forbes, 1849. Mem. Geo!. Surv. United Kingdom, dec. i, 

 p. 8. 



Material. — I studied ii specimens of this species in the British 

 Museum (Natural History) including the specimen figured by 

 Wright (1882, pi. 78, fig. 4). All the specimens came from the 

 same two localities mentioned by Forbes in his original description 

 of the species. The single specimen from Blackdown, Devon, is 

 silicified, but the other specimens, all from Warminster, Wiltshire, 

 are calcareous. 



Shape. — Small, largest specimen 16.5 mm. long, elongate, angular 

 marginal outline, posterior pointed except where blunted by anal 

 groove, sides straight, parallel, very depressed, with greatest height 

 posterior to center; adorally depressed, interambulacrum 5 slightly 

 inflated along median suture. 



Apical system. — Central, tetrabasal, most sutures not visible, geni- 

 tal plate 2 small (text fig. 144) not extending posteriorly between 

 posterior genital plates; four genital pores, right posterior pore 

 slightly displaced laterally and posteriorly ; ocular plates narrow, long. 



Ambulacra. — Petals only slightly developed, very narrow, not clos- 

 ing, extending almost to margin, petals II, III, and IV straight, 

 petals V and I flexuous, curving distally away from each other. 

 Interporiferous zones expanding distally; poriferous zones narrow, 

 pores oblique to each other, inner pore distal to outer, not conjugate, 

 slightly elongated obliquely, inner round (text fig. 144) ; pores beyond 

 petals minute. 



Adoral interambulacra. — Plates large, not alternating, single plate 

 at peristome. 



Periproct. — Supramarginal, midway between apical system and 

 posterior margin ; circular to oval, in deep, flat-bottomed, triangular 

 groove extending to posterior margin. 



Peristome. — Anterior, higher than wide, pentagonal. 



