I20 PHYLOGENY OF FUSUS AND ITS ALLIES. 



Localities: Chaumont, Bos d'Arros. 

 Horizon: Middle Eocene, Calcaire grossier. 



CLAVILITHES DEFORMIS (Solander). 



In the British Eocene. 



(Plate XIII, fig. 14; Plate XIV, figs, i, 3 and 4; Plate XVIII, figs. 7 and 8.) 



1766. Murex defonnis Solander, Brander's Foss. Hants., p. 22, pi. II, figs. 27, 38. 



The species was described by Solander from immature specimens 

 obtained from the Eocene of the Hampshire basin. As has already 

 been remarked the name is best discarded, since the precise relations 

 of the species of which these specimens are the young must always 

 remain doubtful. They probably belong to C. solanderi Grabau, and 

 according to strict ruling Solander's name should have priority. There 

 is, however, the above-mentioned element of doubt, which makes such 

 ruling in this case a questionable expedient. 



In plate XIII, fig. 14, is illustrated a characteristic example of the 

 young Clavilithes comparable to C. defonnis (Solander) as it occurs 

 in the Eocene clays of Barton. 



The protoconch (pi. XVIII, figs. 7 and 8) is much larger and 

 more robust than is even the case in the French species of the genus. 

 Its median whorl has a diameter of nearly 4.5 mm., while the average 

 diameter of the median whorls in the French species is less than 3 mm., 

 seldom exceeding 2.5 mm. In one specimen from Barton the diam- 

 eter of the median whorl of the protoconch was found to be 5 mm. 

 There are, however, specimens in which the protoconch approaches in 

 size more nearly that of the French species. The number of volutions 

 varies from three to nearly four, and they almost always show an 

 irregularity in thickness. A characteristic feature not found in the 

 French species is the flattening of the upper exposed portion of the 

 early whorls of the protoconch, thus giving a sloping or trochiform 

 character to the apex (pi. XVIII, figs. 7 and 8). The apex of the 

 protoconch of the Parisian species is naticoid with the convexity of the 

 whorl unimpaired. 



In the conch the spirals appear before the ribs. The latter are at 

 first mere undulations which, however, quickly become pronounced in 

 most cases. In some accelerated types the ribs never appear, the early 

 whorls being merely spirally striate. The contour of the early whorls 

 is strongly convex. Intercalation of spirals does not appear until 

 after the second volution of the conch. 



There is great similarity in general appearance between the British 

 young shells described as C. defonnis and the yotmg of C. subscalaris 

 and C. scalaris from the Paris Basin beds. 



Localities: Common in the Barton Beds of the Hampshire Basin 

 (M. C. Z. 27783) Bracklesham (M. C. Z. 27765). 



Horizon: Upper Eocene. 



