from the Inferior Oolite of the Cotteswolds. 239 



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

 the Great Oolite of Minchinhampton. 



Trigonia Phillipsi vav. 



Triffonia Phillipsi, Mor. & Lye. Gr. Ool. Monogr. 1853, tab. 6. fig. 1 . 

 p. 62. 



Shell ovately trigonal ; umbones submedian, obtuse, scarcely 

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

 cated ; marginal and inner carinse delicate, tuberculated and 

 small ; area narrow, flattened, striated, divided in its middle by 

 an oblique furrow ; sides of the valves with densely an-anged, 

 elevated, concentric, and finely indented or tuberculated costse. 



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

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

 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. Wurtemb. t. 58. fig. 3. 

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



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

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

 flattened, nearly smooth ; carinse nearly obsolete, rows of tuber- 

 culated costse numerous, directed downwards, tubercles equal, 

 scai'cely separated, placed upon raised costse. 



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, M^m. 

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



Shell somewhat depressed ; umbones recurved ; area flattened, 

 bounded by two distinct narrow finely indented carinse ; costse 

 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 costse are much less raised, more 

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

 the unaided vision. 



Trigonia striata ranges throughout the Inferir.- '^ 

 Cotteswolds, and is abundant a+ t'- " 



