﻿540 DE. WHEELTON HIND ON THE PALEONTOLOGY [Aug. I905, 



Yorkshire Coalfield : above the Hard-bed Coal, Halifax. South- 

 Wales Coalfield : under the Pare well Rock, Glan Rhymney. 



In beds of Millstone-Grit age : Stibden (Yorkshire) ; Ipstones 

 (Staffordshire). 



Gastriocekas Listekt (Martin). 



This species has only been noted by Mr. John Ward as occurring 

 in the Cheadle Coalfield ; but the specimens that he figured should 

 be more correctly referred to Gastrioceras carbonarium. I have no 

 personal knowledge of its occurrence in North Staffordshire. 



Pleuronautiltts costatfs, sp. nov. (PI. XXXYI, figs. 5, 5 a, 

 & 5 b.) 



Specific characters. — Shell discoidal, composed of three 

 rapidly-enlarging, closely-applied, quadrate, ribbed whorls. Um- 

 bilicus large, showing nearly the whole of the whorls. 



The whorl is almost square, but somewhat narrower at the 

 periphery than at the umbilical margin ; the periphery is very 

 slightly concave, each margin being raised into a ridge, a character 

 absent in the cast ; the sides are very slightly concave above, convex 

 below. The umbilical slope is smooth, moderately rapid, rounded 

 in the young, subangular in the adult. 



The body-chamber is large, and occupies apparently about one- 

 third of a whorl. The aperture is not seen, but there must have 

 been a broad and deep hyponomic sinus on the periphery. I can 

 give no details of the chambers (camerae). 



Siphuncle small, subcentral, somewhat nearer the periphery than 

 the lower margin. 



Nepionic stage not free, contiguous to the next whorl. 



Ornament. — The shell is adorned with broad, arched costae, 

 separated by broad sulci, except over the body-chamber, which is 

 smooth. These costae rise on the umbilical margin of the whorl, 

 and are somewhat swollen at the junction of the umbilical and 

 lateral surfaces. They become broader and flatter, and arched 

 somewhat forwards, and are inflated again at the junction of the 

 lateral surface with the periphery. The costae are more arched in 

 the younger portion of the shell. 



The sides of the shell are covered with minute lines of growth ; 

 on the periphery these lines show a deep, broad sinus with the 

 concavity directed backwards. The nepionic stage is devoid of 

 costae, and has well-marked parallel striae. 



Dimensions. — The most complete specimen has a diameter of 

 84 millimetres. 



Locality. — North-Staffordshire Coalfield: below the Gin-Mine 

 Coal. 



Observations. — This species is founded on one fairly-complete 

 specimen and several fragments, casts, and crushed examples. I have 

 compared them with Pleuronautihts armatus (Sow.) and PI. falcatus 

 (Sow.). In the former the costae are fewer, more sigmoid ; in the 

 latter the costae are more numerous and more regular in character, 



