12 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Mar. 24, 



26. Ammonites hypeebolictjs, Leckenby (Simpson, MS.). 

 PI. II. fig. 4:a, 4:b. 



This, on the contrary, is so much thicker than Am. Chamusseti as to 

 be nearly globular. The outer whorl entirely envelopes the umbi- 

 hcus ; and the keel, which is not crenulated, is nearly obsolete. 



27. Ammonites glabellas, Leckenby (Bean, MS.). PI. II. fig. 5a-5c. 



Discoid; sides of the whorl smooth, or nearly so, having only 

 faint distant undulations, which are most conspicuous towards the 

 keel : back, a sharp keel becoming rapidly obtuse with age ; aper- 

 ture elliptical, deeply indented by the succeeding whorl. 



Locality. Scarborough Castle E.ock. 



28. Ammonites conteeminits. Bean, MS. 



Discoid ; whorls flatted, their inner margin perpendicular, their 

 outer margins rounded towards the back : ribs sigmoidal, bifurcating 

 in the middle of the whorl, and terminatiug near the outer margin ; 

 keel sHghtly elevated ; aperture ovate, slightly indented by the suc- 

 ceeding whorl. 



Localities. Scarborough Castle Rock, and near Gristhorpe Bay. 



29. Ammonites bipartitus, Zieten. 

 Locality. Scarborough Castle E.ock. 



30. Ammonites Baugieei, D'Orbigny. 

 Locality. Near Gristhorpe Bay only. 



The last two species agree exactly with the descriptions and 

 figures of D'Orbigny. 



Pleueotomaria arenosa, Leckenby (Bean, MS.). PL III. fig. la, 16. 

 Trochus arenosus, Bean, MS. 



Shell conical, imperforate ? ; whorls (6 or 7) flat, transversely and 

 longitudinally ribbed, giving the shell a somewhat decussated ap- 

 pearance ; at the lower portion of each whorl is a prominent band, 

 formed of four strongly undulating nodular ridges, then two finer 

 lines ; these are succeeded by a smooth space, along the centre of 

 which is the raised sutural band, somewhat crenulated ; the re- 

 mainder of the whorl occupied by eight or nine transverse wavy 

 lines, crossed by oblique longitudinal finer ones, which are more 

 prominent at distant intervals. 



This species is closely allied to the Pleurotomaria Galathea, D'Orb. 

 Pal. Franc. Terr. Jurassique, pi. 423. fig. 1-4. 



Locality. Castle Hock, Scarborough. 



Pleurotomaria striata, Leckenby (Bean, MS.). PI. III. fig. 2a, 26. 

 Cirrus striatus. Bean, MS. 



Shell depressed, umbilicate? ; whorls four, tabulated ; keel slightly 

 prominent, transversely ridged and crossed by numerous very fine 

 oblique, irregularly undulating, raised lines, which pass uninter- 

 ruptedly over the keel. 



Locality. Castle Rock, Scarborough. 



