SF]ARLESIA COSTIFER. 1:10 



Fossil : Waltonian Crag : Little Oakley. 

 BemarJcs. — In this variety, of Avlncli I have obtained several specimens, 

 the longitudinal ribs are numerous, fine, and inconspicuous, extending nearly 

 to the base of the shell ; the spiral costge are further apart and become granulate 

 where they cross the latter, the shell presenting a cancellate appearance. 



Var. crassa, nov. Plate XIII, fig. 1 1 . 



Dimensions. — L. 4-2 mm. B. 24 mm. 



Distribution. — Not known living. 



Fossil : Waltonian Crag : Little Oakley. 



BemarJcs. — The shell figured under the above name, one of several I obtained 

 at Oakley, differs from either of the more common forms of /S^. costifcr. It is a 

 coarse strong shell, the whorls being somewhat angulated above, forming a shelf 

 below the suture ; the body- whorl is proportionately larger and wider than in the 

 type, and is excavated below ; the suture is deep, and the canal very short. 



Var. islandica, nov. Plate XIII, figs. 7 — 10. 



1887. JJrosalpinx costifer, var., Morcli aud Poulsen, plates aud MS. list in tlie Geological Museum, 

 Copenliagen, no. 7, pi. i, fig. 7 (unpublished). 



Varietal Characters. — Shell slender, fusiform ; whorls 7, decidedly convex, the 

 last five-eighths the total length, excavated below ; ornamented by about twelve 

 prominent longitudinal costee, rounded and narrower than the spaces between 

 them, and by fine spiral lines ; more delicately sculptured than in the type form of 

 L. costifer ; spire elongate ; suture deep ; mouth oval, and shorter than in the 

 latter, having a well-marl^ed canal, which turns to the left ; outer lip thin. 



Dimensions. — (Of specimen from Iceland) L. 40 mm. B. 18 mm. (Of the Crag 

 specimen) L. 30 mm. B. 14 mm. 



Distrihution. — Not known livino-. 



Fossil: Waltonian Crag : Walton-on-Naze, Little Oakley. New- 

 bournian : Sutton. Pliocene : Iceland. 



Remarks. — This shell, with that next to be described, seems to be separated 

 from the typical ^S'. costifer by its delicate sculpture, its more slender form, and 

 its more distinct and somewhat longer canal. Comparing the graceful Icelandic 

 fossil with the coarser shells of the Crag one might regard them as specifically 

 distinct; we find specimens in our own deposits, however, which tend to connect 

 the two. The absence of the prevalent Crag varieties of S. costifer from Iceland 

 is important because it confirms the separation of S. Bjornsoni (described 

 below) from that species in the Icelandic deposits, and by implication in our own. 



