84 PHYLOGENY OF FUSUS AND ITS ALLIES. 



coarse rounded ribs cancellated by simple spirals which 



characterize all the succeeding stages. These ribs are 



separated by interspaces which are not infrequently 



twice the width of the ribs. The spirals are simple, 



but between the ribs and on the spindle they are 



nodulose. The aperture is somewhat contracted, and 



the interior of the whorl is Urate. The spindle is 



relatively shorter than in typical Falsifiisiis, thus giving 



the shell something of a Latims-like appearance. 



The protoconch of this species resembles somewhat 



j: 9 >,v^7;. that of Pwopsis perula Aldrich from the Midwav beds 

 fusus" apicalis. j i t 



(After John- of Matthews' landing. 



son.) Locality: Alabama Bluff, Trinity River, Houston 



County, Texas (Johnson, Phil. Acad. 6878). 

 Horir.on: Eocene, Lower Claiborne. 



FALSIFUSUS (?) SERRATUS (Deshayes). 



(Plate I, figs. 9, 10, 14.) 



1824. Fiisus scrratus Deshayes, Coq. Foss. Env. Paris, t. 2, p. 515, pi- 75, figs. 



12, 13. 

 1866. Fusus serratus Deshayes, Anim. sans vert., p. 253. 

 1889. Fusus serratus Cossmann, Cat. Coq. Foss., p. 178. 



The protoconch of this species consists of several volutions and 

 merges into the conch without any definite line of demarkation. There 

 are in all nearly two smooth volutions, the first being swollen but de- 

 pressed, with the apex buried in the succeeding whorl. It gradually 

 increases in size, this increase continuing into the second whorl. On 

 the lower part of the second whorl, above the suture, a sharp strongly- 

 marked revolving line or spiral occurs, which lies just above the 

 suture. After a volution or more it disappears. On the third whorl 

 faint costje or riblets occur above this line. These are smooth and 

 not cancellated by revolving spirals. They are slightly concave for- 

 ward, at the same time they slope obliquely forward from the upper to 

 the lower suture. Towards the end of the third volution these ribs or 

 costse become stronger and more vertical, and finally they become can- 

 cellated by revolving spirals. The whorls up to this point are rounded. 



It is very difficult to state in this case where the protoconch stops 

 and the conch begins. In a few specimens a faint growth line appears 

 after the first volution or volution and a fourth. This may mark the 

 end of the protoconch, which in that case is smooth and without 

 ornamentations. If this is the case the nepionic. stage of the shell is 

 characterized at first by a smooth half whorl or more, followed by a 

 portion of a whorl with simple ribs, and later by the normal round- 

 ribbed whorls with well-developed spirals. It seems best on the 

 whole to regard this unusual type of ornamentation as belonging to the 



