Mr. J. Morris on some new species of the genus Aucyloceras. 33 



septa appear to be more simple than in the cretaceous species, the 



superior lateral lobe is a little longer than the dorsal one, the in- 

 ferior lateral lol)e beinj; nearly equal in length with the superior 

 tlicse however vary slightly, aecorchng to the period of growth. 



To Mrs. Lowe of Chippenham we were indebted for our know- 

 ledge of this interesting species, by whom it was obtained from 

 the Kelloway rock near that town, during the progress of the 

 works for the Great ^^'estern Railway. The tigiu'es are executed 

 from specimens in the collections of C. Pearce and S. P. Pratt, 

 Esqrs. 



Ancyloceras costatus. (PI. VI. fig. 4. a, b.) 



A. testa elongata, transversim oblique costata, costis approximatis 

 obtusis, per dorsum interruptis ; dorso rotundato ; apertura ovali. 



On the produced part of this shell the ribs are simple, obtuse, 

 broader than the intervening sulcations, and increasing slightly 

 in thickness from the ventral to the dorsal margin, where they 

 are interrupted by a smooth space along the median line of the 

 back. The spiral volutions have not yet been discovered, and 

 the foliations of the septa are not shown in the sjiecimen figured. 

 This species bears some resemblance to the A. furcatus (d^Orb.) 

 in the abrupt termination of the costae on the dorsal margin, but 

 the ribs are of greater relative thickness and not furcate as in 

 that species. 



From the inferior oolite near Bridport, in the collection of 

 Channing Pearce, Esq. 



Ancyloceras Waltoni. (PI. VI. fig. 5. a, h, c.) 



A. testa elliptica, transversim a?qualiter costata, costis subacutis ; 

 anfractibus rotundatis ; apertura ovali. 



The surface of this shell is covered with a regular series of 

 somewhat acute ribs, which are slightly arched on the ventral 

 portion and arc interrupted on the dorsal margin, where they ter- 

 minate with a bluntish tubercle. The superior lateral lobe is as 

 long as the dorsal one, the inferior lateral lobe is as wide and 

 even longer than the superior one. From the inferior oohte 

 near Bridport, in the collection of ^V. Walton, Esq. These sj)eci- 

 mens so closely resemble a species obtained by Mv. Bimbury 

 from the inferior oolite of Calvados, that I feel some difficulty in 

 assigning to it a specific name, in consequence of Mons. d'Or- 

 bigny stating that one species only, the Ancyloceras annulatus, 

 is found in that deposit, of which I have not seen either a figure 

 or description. Should it, however, prove to be a distinct species, 

 I have proposed the name of A. JVnltoni, as a tribute of respect 

 to a gentleman who has assiduously cultivated the study of the 

 oolitic fossils. 



Ann. cV May. N. Hist. Vol. xv. D 



