332 GEOLOGICAL SURVEY OF TEXAS. 



are subangular, with a row of obscure elongated nodes, which, are more marked 

 on the shell than on the cast, and better marked on one side than on the 

 other. The shell has fine strise of growth almost straight or only slightly 

 concave on the sides and bending backwards on the abdomen to form broad 

 and apparently deep sinuses. These sinuses are, however, much broader in 

 proportion and not as deep apparently as those in the strise on the abdomen 

 of Tern, crassus. 



The sutures are only slightly concave on the sides and have very broad and 

 extremely slight lobes on the abdomen. They are numerous, and the inter- 

 spaces of the air chambers quite narrow. The tubercles are more obscure 

 than in other species on the cast and also less prominent on the shell ; the air 

 chambers are also narrower than usual in species of similar proportions. It 

 is similar to T. conchiferus in the slight character of the nodes and transverse 

 section of whorl, but the increase by growth is less, in T. conchiferus the 

 nodes extend internally across the longitudinal axis of the whorl, whereas 

 in this species they extend parallel with that axis, and the shell is thicker 

 in conchiferus. 



It is closely similar to Temnocheilus coronatus as figured by De Koninck* in 

 his Calcaire Carbonif ere ; but our species has an abdomen somewhat more de- 

 pressed and very much broader in proportion to the abdominal and dorsal diam- 

 eter at the same age, and the nodes are less prominent. It is similar to Tern, 

 latus and Winslowi in the transverse section of the whorls and umbilici, but 

 the nodes are more numerous and much smaller. It differs from Tern. Forbe- 

 sianus in having a much broader whorl at the same age and much deeper and 

 more funnel-like umbilici, the nodes are not so heavy and are closer together, 

 but the sutures are similar in both. No living chamber was observed. Po- 

 sition of siphuncle is unknown. Fig. 26 is in part restored. 



* Ann. du Mus. d'Hist. Nat. de Belgique, II, PL 24, Fig. 2. 



