OF CONCHOLOGY. 



21 



Mont.), and possess a long anterior canal, could form a small 

 group, designated by Conrad Anchura. 



" 3d. Broad winged shells with only a single point to the 

 posterior external termination, as Host. Orbignt/ana, Pictet, or 

 Host, jycqyilionacea, Goldf., might be designated under a separate 

 name. 



*' All these three forms are generally ornamented by trans- 

 verse ribs. 



"4th. Species with slightly dilated wing, soon dividing into 

 two or three long extremities, carinated and usually spirally 

 striated whorls, etcet. — as the long known Al. myurus, Desh., or 

 Al. Icevigata, Morris, might be referred to Tessarolax,Ga,hh. 



" 5th. To retain under Ajjorrhais only those species which 

 have a broad dilated wing from the base, terminating exteriorly 

 in as many points as there are keels on the exterior side of the 

 wing, which ought in all cases to extend to the exterior margin 

 of the wing, as in Ajj. Dupmiana, D'Orb., or Aj). [Ohenopus) 

 atractoides, Desh. 



" 6th. The Jurassic DiartJiema paradoxa, Desh., forms a sepa- 

 rate genus, somewhat allied to Ranella. 



7th. Spinigera, D'Orb., ought probably to be classed here 

 rather than with Ranella." 



For convenience I shall take up each division seriatim : 



1st. As I have already shown, Alan'a should be applied only 

 to those species possessing a varix. Neither A. hamus nor A. 

 rhinoceros possess varices, and I do not consider the fact of one 

 rather than two or more processes on the lip of generic value, 

 especially since such species as A. hamus show a very percepti- 

 ble tendency to a second process, in the existence of a carina on 

 the whorl, and an angle on the margin of the lip at the termina- 

 tion of the carina. I shall therefore place these shells in Di- 

 croloma, at most as a subgeneric division. 



2d and 3d. Anchura, Conrad, must include all those creta- 

 ceous shells of a long fusiform shape, without varices or arrests 

 of groAvth of any kind, with a thickened inner lip, and with the 

 outer lip expanded, broad or narrow, bearing a projecting pro- 

 cess posteriorly, and (or without) one anteriorly on the outer 

 margin. This genus differs from the preceding, as well as from 

 its ally Alaria, in the inner lip being always more or less and 

 usually strongly thickened, while in those genera the inner lip 

 is very thin and generally obsolete. 



The details of form of the outer lip must take a secondary 



