4l6 STUART IVELLER 



GASTROPODA. 



Lagena? antarctica, n. sp. Plate I, Figs. 4, 5. 



Description. — Shell rather small, fusiform, with about four volutions, the 

 periphery forming a sharp revolving keel. Spire elevated, its height but little 

 less than that of the outer volution. From the revolving keel the surface of 

 each volution slopes abruptly to the suture below, the upper surface of the 

 volution has a much longer concave slope to the suture above. The outer 

 slope of the last volution drops abruptly from the periphery, is then concave 

 for a short distance and then continues in a nearly straight or slightly convex 

 line to near the anterior extremity of the shell where it is again concave. 



Surface of shell marked by fine lines of growth which bend backward in 

 passing from the suture to the peripheral keel. 



The dimensions of the only specimen observed are: total height ig.S"""", 

 diameter of last volution on the periphery ii""". 



— Walker Museum, Pal. Coll. No. 9713. 



Remarks. — This species is established upon a single specimen which preserves 

 the mould of the exterior and a cast of the interior of the shell. It is a rather unusual 

 form of gasteropod shell in Cretaceous faunas and agrees most closely with a species 

 described as L. secans Stol., from the Upper Cretaceous of southern India. The 

 antarctic species^ here described may be distinguished from the Indian species by the 

 absence of the angular revolving rib upon the outer volution below the peripheral keel. 

 In other respects the two species are much alike. 



Tubulostium callosum Stol. Plate I, Figs. 6-17. 



1898. Tubulostium callosum Stoliczka. Pal. Ind,, "Cret. Faun, of S. Ind , 

 Gasteropoda," p. 241. PI. XVII, Figs. 26-32. 



Description. — Shell sinistral, thick and rugose, more or less nearly 

 discoidal in form, sometimes with a low spire, aperture circular, entire. Volu- 

 tions exceedingly irregular, apparently three or four in number, the inner 

 ones being eroded in all specimens observed so that their number, cannot be 

 accurately determined. The peripheral portion of the shell is much thick- 

 ened, the thickened portion being divided into three strong, more or less 

 irregular revolving ribs ; the shell is also marked by conspicuous, irregular 

 lines of growth. 



The dimensions of the best preserved specimen are : maximum diameter 

 17"""', height of outer volution 8""", diameter of aperture 3""". 



— Walker Museum Pal. Coll. No. 971 1. 



Remarks. ^^'^\% little shell has been identified with a south Indian species 

 although none of the Indian specimens which have been illustrated are as nearly 

 discoid in form as some of the Antarctic ones. The Indian specimens, so far as illus- 

 trated at least, agree most closely with Fig. 17 upon the accompanying Plate I. 

 The four specimens here illustrated show a regular gradation from the more discoid 

 to the more heliciform shells, and without doubt all are members of a single species. 



^ Pal. Ind., "Cret. Faun, of S. India Gasteropoda," p. 138, pi. 11, f. 20. 



