from the Inferior Oolite of the CotteswoJds. 239 



common, but the shell itself is rare ; it has also been found in 

 the Great Oolite of Minchiuhampton. 



Trigonia Phillipsi var. 



Trigonia Phillipsi, Mor. & Lye. Gr. Ool. Monogr. 1853, tab. 6. figi 1 . 

 p. 62. 



Shell ovately trigonal ; umbones submedian, obtuse, scarcely 

 recurved, anterior border rounded, posterior border short, trun- 

 cated ; marginal and inner cariuse delicate, tuberculated and 

 small ; area narrow, flattened, striated, di\dded in its middle by 

 an oblique fun*ow ; sides of the valves with densely arranged, 

 elevated, concentric, and- finely indented or tuberculated costae. 



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

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

 rather indistinct, and their junctions with the posterior and more 

 curved portions form a kind of angle. 



A more detailed description will be found in the monograph 

 above referred to. 



Trigonia signata, Ag. 



Syn. Trigonia clavellata, Zeiten, Petref. Wvu-temb. t. 58. fig. 3. 

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



The most elongated and depressed of the Clavellata ; the um- 

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

 flattened, nearly smooth ; carinae 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; Agassiz, Mem. 

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



Shell somewhat depressed ; umbones recurved ; area flattened, 

 bounded by two distinct narrow finely indented carinae ; costaj 

 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 HiU near Stroud. 



