4 FOSSIL MOLLUSCA OF THE CHALK. 



B. Testa sub-cylindricd, inferne rotundatd, acuminata; superne rotundato-quadratd ; 

 antice, later aliter que lined impressd leviter notatd. 



Shell sub-cylindrical, slightly flattened both on the front and sides of the upper part, 

 rounded below, and tapering gradually to a blunt point ; with a slight furrow down the 

 upper part in front, and a slight furrow down the upper part of the middle of each side ; 

 opening oval. 



Length, 2 inches ; greatest breadth, -f^i\^^ of an inch. 



Found by Mr. Saxby, in the Chloritic Marl of Bonchurch, in the Isle of Wight ; found 

 also in the Red Chalk of Yorkshire, and in the Gault of Folkstone. 



This species is usually confounded with Belemnites minimus of the Gault, from which 

 it is to be distinguished by a more cylindrical form, the slightly squared oval opening, and 

 shortness of its lateral furrows. B. minimus on the contrary is spindle-shaped, with a round 

 opening, and a double line impressed on each side, which reaches nearly to the point. 



Professor Phillips first pointed out the necessity of separating the two species (' Geol. 

 Yorksh.,' vol. i, p. 46), and called this one B. Listen, although that name had previously 

 been applied by Dr. Mantell to the other species. Lister undoubtedly had the two species 

 before him when he wrote ; but his name having been since restricted by all authors to 

 the common Gault species, which has been called indiscriminately B. minimus and B. 

 Listeri, it would increase the confusion to apply either of those names to this species, 

 which may therefore pass under M. D'Orbigny's name of B. ultimus. 



Plate I, fig. 17, a, b, c. Three views of Mr. Saxby's specimen, from the Chloritic 



Marl of Bonchurch : the point having been worn away, its 

 outline is restored from another specimen. 



Belemnitella, D' Orhigny. 



Animal unknown, enclosing a straight, elongated, conical, or fusiform calcareous 

 shell or guard, more or less pointed below, and pierced above with a conical cavity or 

 alveolus, in which is lodged the phragmacone, a hollow horny cone, divided into chambers 

 by nearly horizontal septa, which are perforated on the anterior or ventral margin by a 

 siphuncle. Wall of the alveolus divided on the anterior side by a perpendicular slit, which 

 remains open above, but is gradually closed below, where its place is marked by a groove 

 on the outside of the shell, and a corresponding groove on the inside of the alveolus. 

 Back of the exterior of the shell marked by two longitudinal depressions, which in some 

 species are connected with complicated vascular impressions. 



The remains of Belemnitella hitherto found in the Chalk, in this country, are limited 

 to the calcareous shell ; in addition to which portions of the phragmacone are preserved 

 in the specimens of B. mucronata found in the Cretaceous Sandstone of Maestricht and 

 Ciply, 



