Sone new Upper Greensand Gasteropods. 291 



with spaces as wide as those on the side ; in the middle are 

 four close small striae, and on the inner part two wider. A 

 strong elevated keel, having about twenty small tubercles on 

 the last whorl, forms the margin of the umbilicus. Umbilicus 

 large, as wide as the base, marked on each whorl with several 

 (about six or eight) prominent striae. Mouth externally five- 

 sided, internally round. 



In another state of preservation, this species would be referred 

 to a different genus. It commonly happens that the outer shell 

 is removed, and the nacreous layer exhibited; this is round, 

 smooth, marked with lines of growth, yellowish in colour, and 

 has every appearance of being external. 



The general affinity of this shell with Solarium neocomiense 

 (D'Orb.) is very great ; but it is less depressed, differently stri- 

 ated, has no keels, a striated umbilicus, &c. 



Not uncommon. Specimens with the shell preserved are 

 contained in the Univ. Mus. and that of Mr. Carter. Casts in 

 all Collections. 



This shell is only provisionally referred to Gihbula : the genus 

 to which it belongs is not yet constituted. 



Pleurotomaria semiconcava. PI. XI. fig. 17. 



Shell conical, wider than high, formed of whorls (five) which 

 regularly increase in size. The whorls are concave, with a 

 projecting sutural angle. The last whorl is high, and divided 

 by the strongly elevated keel of the sinus into an upper con- 

 cave part and a lower flat side, which rounds off into the 

 slightly convex base. The sinus forms the line of suture. 

 The concave part has about six narrow striae; a similar num- 

 ber marks the space below. The base is striated. Aperture 

 rhomboidal. Umbilicus as wide as the base. In the cast 

 the hollow part of the whorl is flat and oblique, with a narrow 

 flattened space above. 

 The spiral concavity and angular body- whorl fully distinguish 



this species from every other. 

 Rare. Woodwardian Museum. 



Crepidula Cooksonia. PI. XI. fig. 18. 



Shell small, nearly as high as long, and three-fourths as high as 

 wide, regularly inflated, nearly symmetrical, thin. 5ase 

 transversely ellipsoid, not flat. Apex small, mesial, and above 

 the middle of the posterior side. Outline of the anterior side 

 of the shell oblique, rounding, top lounded ; posterior outline 

 nearly perpendicular. Attachment of the lamina narrow, 

 about a third the width of the shell, consisting of upright 



