EASTERN PROVINCE SOUTHERN REGION SPECIES. 4M 



goageshaped cusp, bearing a still broader cutting edge (see d, wLere 

 the form of the cusp of the side teeth is shown by the profile). The 

 side teeth run rapidly and obliquely backward from the central tootli, 

 thus giving a chevron-like arrangement to the membrane. The teeth 

 are crowded together both longitudinally and transversely, excepting 

 as they approach the outer edges of the membrane, where they are 

 much more separated. 



I have used the term side teeth instead of lateral and marginal teeth, 

 because it is difficult to decide which of these types they properly are. 

 Taking into consideration the fact of there being distinct lateral 

 teeth in the allied species, L. virgineus, and that the marginals of that 

 species resemble the side teeth of L. fasciatus, I am inclined to believe we 

 should consider all the side teeth of fasciatus as marginals. In this case 

 we must consider that the lateral teeth are entirely suppressed. The 

 marginals, as I have decided to call them, are of the same tyi)e as the 

 centrals. The base of attachment is, however, asymmetrical by the 

 suppression of both upper and lower inner lateral expansions ; the up- 

 ];er margin is simply squarely truncated. Above the center of the 

 base of attachment springs from its surface the gouge-shaped, rounded, 

 gradually expanding cusp, reaching nearly the lower margin of the 

 base of attachment, and produced into a still more expanded, bluntly 

 truncated cutting edge (one cannot call it a cutting point), which iiro- 

 jects far beyond the lower margin of the base of attachment on to 

 the teeth of the next tranverse row, and is also greatly expanded on 

 the outer side, so as to overlap the adjoining tooth* This cutting edge 

 is slightly incurved at its center. There is one point of difference be- 

 tween the central and adjoining marginal teeth which is very marked; 

 in the centrals the lower margin of the base of attachment is more ex- 

 panded than the cutting edge, the reverse of which is found in the 

 marginals. 



The marginals retain this general form to the extreme edge of the 

 membrane, but they decrease greatly in size upon the edge. The 

 outer marginals have to their cusps a small side spur, gouge-shaped 

 as the cusp itself; the extreme marginals have such a spur at either 

 side. In both cases the cutting edge springs from the outer side of 

 this side spur, which must be considered as representing the side 

 cusps of the usual Helicidce type of dentition. I have elsewhere (Ann. 

 Lye. :N^. H. of N". Y., XI, 39) shown that this type of tooth is but a 

 modification of the usual type, brought about by the expansion, bluntly 



