﻿214 BRITISH FOSSIL CEPHALOPODA. 



symmetry. The section is transverse in the ratio of 11 to 6, reniform in shape by 

 the overlapping of the previous whorls. The surface has obliquely-marked ridges, 

 curving backwards in a sinus on the front. There are lines of growth parallel to 

 these and longitudinal striations, according to Conrad, which, however, have not 

 been observed by Hall. The specimens are from the Hudson River group. 



General Description. — A single small fragment has formed the subject of all the 

 above English references, except an allusion by Salter to there being better speci- 

 mens, the descriptions being adopted from Hall. This specimen shows no external 

 ornaments, but has a well-marked constriction on its surface, which forms a sinus 

 on the convex side. The siphuncle is internal, and the convexity of the septum 

 moderate. The section is transverse, reniform, and nearly twice as thick as it is 

 broad. The shape of the suture on the front is not seen, nor is it stated by Hall. 

 An admirable small specimen from the Lower Llandovery of Golengoed, marked as 

 Lituites undosus in the Catalogue of the Museum of Practical Geology (fig. 7), 

 shows 2^ whorls, of reniform section. The measures agree generally with the 

 above. The surface has low, irregularly striated ribs, as numerous as the septa, 

 curving gently backwards till near the convex side, where they make a deep sinus, 

 cutting 3 septa ; these ornaments are quite superficial, and leave the cast smooth. 

 The siphuncle is conspicuous and internal. The septa are 33 in number in the last 

 whorl, and have a backward wave on the flattish front. Other specimens are 

 external casts only : one reaches a diameter of 3^ inches, and seems to be more 

 evolute ; another shows beautiful epidermids, curving backwards and passing 

 straight across the front. 



The specimen to which the name Lituites Hibernicus has been applied (fig. 8) 

 agrees with the rest in its general aspects. It has a ratio of increase 1.33 and the 

 last whorl .33, the inner whorls being somewhat concealed. The only difference 

 indicated by Salter is that the sutures have a sinus on the front. The lines taken 

 for sutures in the specimen may more probably be impressed lines of growth, as 

 shown by other examples, for they cannot be traced all round the whorl, and, even 

 if they were septa, the specimen would still remain within the limits of the species. 

 This specimen shows the form of the aperture, which is bounded behind by a 

 constriction and then has an outward-turned lip. 



Varieties. — An example associated with the others from the Bala Beds, in the 

 Museum of Practical Geology, has so different a shape of section, that it must be, at 

 least, reckoned as variety trapezoidalis if it is not worthy of a specific name. The 

 section is very flat on the front, and somewhat so on the sides, with no indentation 

 within. It is transverse in the ratio only of 10 to 9. 



Relations. — This differs from Trocholites anguiformis by the much more trans- 

 verse section, and agrees very well with the American species to which it has been 

 referred. 



