REV. J. E. CROSS ON THE GEOLOGY OF N.W. LINCOLNSHIRE. 129 



owing to the posterior side being more produced or elongated. Ex- 

 teriorly the shell seems to have been minutely reticulated, coarsely on 

 the posterior side of the umbo, the anterior being nearly smooth. 



The numerous figures of species of this genus given by continental 

 authors do not aid me in referring this form to any known species ; 

 and although this and G. Rolandi are small shells, they are evidently 

 mature in age, the thickness of the shell, development of the 

 dental system, and markings on the shell attesting this ; and no 

 Cucullcece in the Inferior Oolite of the west or south-west of Eng- 

 land resemble them. 



Loc. Santon. Formation. Inferior Oolite. 



Astarte. 



Abundant as the species of Astarte are in the Oolites of England, 

 Mr. Cross has found and determined another form distinct from any 

 thing yet known ; and small as the specimen is, it appears to be a 

 mature shell. The type is remarkable, and must be rare, as no 

 kindred species has yet occurred in our Lower Secondary rocks. 

 "We possess only one valve of this interesting shell. 



Astarte divaricata (Cross, MS.), Ether. PI. V. rig. 1. 



Shell inequilateral, small, ovately trigonal, as broad as long; 

 umbo acute ; inner edge of valve ornamented by a row of minute 

 dot-like tubercles or denticulations, which extend from anterior to 

 posterior adductor-muscular scars. Outer surface marked with 

 divaricating costae or ribs, 12 or 14 in number, reckoning the 

 divarication from the umbo to the centre of the ventral edge ; the 

 line of divarication commences near the umbo, and extends to the 

 centre of the ventral border ; both on the anterior and posterior 

 sides or edges of the shell the ribs are strongly crenulated or folded, 

 especially on the anterior side, where they are almost spinose; 

 the surface of the costae is ornamented with delicate striae at right 

 angles to them, the delicate lines passing over and between the ribs. 



Had this been a Pecten instead of an Astarte, we should not have 

 ventured to thus notice it, fearing that the other or opposite valve 

 might have been very different ; but as both valves in Astarte possess 

 the same ornamentation it little matters. Our valve being a left 

 one, we can only judge of the anterior tooth in the right by the 

 corresponding pit in the left, which evidently received a long and 

 deep tooth. 



Loc. Santon. Formation. Inferior Oolite. 



EXPLANATION OF PLATE V. 



Fig. 1. Astarte divaricata, sp. n. Twice natural size. 



2,. 2 a. Cucidlcea santonensis, sp. n. Twice natural size. 



3. Cucullcea Eolandi, sp. n. Natural size. 



4. Tancredia ferrea, sp. n. Natural size. 



5, 5 a. Tancredia liassica, sp. n. Natural size. 



6, 6#. Hippopodium ferri, sp. n. Natural size. 



