from the Inferior Oolite of the Votteswolds. 261 



The present variety of the Lincolnshire shell, and of which I 

 only know two examples, has the anterior portions of the costs 

 rather indistinct, and their junctions with tne posterior and more 

 curved portions form a kind of angle. 



A more detailed description will be found in the monograph 

 above referred to. 



Trigonia siynata, Ag. 



Syn. Trigonia clavellata, Zeiten, Petref. Wurtemb. t. 58. fig. 3. 

 T. signata, Ag. Mem. sur les Trigondes, p. 48. pi. 3. fig. 8. 



The most elongated and depressed of the Clavellata* ; the urn- 

 bones are not prominent nor recurved ; the area is lengthened, 

 flattened, nearly smooth ; carina? nearly obsolete, rows of tuber- 

 culated costae numerous, directed downwards, tubercles equal, 

 scarcely separated, placed upon raised costae. 



Rare : position the lower or Ammonitiferous beds of the Infe- 

 rior Oolite near Stroud. 



Trigonia striata, Sow. 



Trigonia striata, Sow. Min. Con. tab. 237. fig. 1-3 ; Agassii, Me*m. 

 sur les Trigonees, pi. 4, fig. 10-12. 



Shell somewhat depressed ; umbones recurved ; area flattened, 

 bounded by two distinct narrow finely indented carinae ; costae 

 raised, numerous, concentric, deeply serrated, and varying in their 

 number. 



Trigonia Phillipsi, Mor. and Lye. Gr. Ool. Mon. would easily 

 be mistaken for this species, but the Lincolnshire shell is shorter, 

 the umbones not recurved ; the costae are much less raised, more 

 closely arranged, and so finely serrated as to appear smooth to 

 the unaided vision. 



Trigonia striata ranges throughout the Inferior Oolite of the 

 Cotteswolds, and is abundant at Rodborough Hill near Stroud. 



Trigonia subglobosa, Mor. & Lye. 



Trigonia subglobosa, Morris & Lycett, Gr. Ool. Monog. Bivalves, 

 1853, tab. 5. fig. 21. p. 55. 



Shell nearly circular, convex ; umbones recurved ; area small, 

 with three tuberculated carinae; costae large, closely arranged, 

 angulated, their posterior portions forming a few large perpen- 

 dicular varices. 



It occurs in the freestone beds near Nailsworth ; also in the 

 Great Oolite : in both formations it is somewhat rare. 



