116 



increase in size anteally, where they also curve more or less 

 horizontally, towards the anterior border. 



Obs. T. formosa is a very common form in the Cephalopoda- 

 bed at Bradford Abbas, and in the Sands below, of the Inferior 

 Oolite. 



TRIGONIA STRIATA, Miller, plate i., fig. 7. 



MONO. BEIT. Foss. TEIGONLE, Lycett, Pal. Soc., p. 36, plate 5. figs. 68. 



Shell sub quadrate, short, moderately convex, umbones small, 

 erect, and only slightly recurved ; anterior side short, somewhat 

 truncated, lower border curved elliptically, superior border short, 

 horizontal, forming a considerable angle with the wide truncated 

 extremity of the area, which is traversed mesially by an obscure 

 furrow, the transverse striations are very regular and minute 

 even to the apex ; the escutcheon is narrow, lengthened and 

 much depressed, its superior border is considerably raised; the 

 other portion of the surface has about twenty-two narrow^ 

 obliquely curved, and elevated costse. The most remarkable 

 features of this species are the short sub-quadrate figure, and 

 the large size of the area. 



Obs. This Trigonia occurs in the zone of Ammonites Hum- 

 phriesianus, at Burton Bradstock, and is not found in the northern 

 extension of the series. 



TRIGONIA SIGNATA, Ag. 



MONO. BEIT. Foss., TEIGONI., Lyc. } Pal. Soc., p. 29, pi. ii., figs. 1-3. 



Shell ovately elongated, sub-trigonal depressed; umbones 

 antero-mesial, email, and not prominent nor recurved, but rarely 

 they are erect and recurved ; the anterior side is moderately pro- 

 duced and rounded ; both this and the lengthened lower border 

 are curved elliptically ; superior border straight and lengthened, 

 and rarely somewhat concave; area wide and flattened, its 

 posterior extremity is compressed and somewhat truncated, 

 bounded by two delicate minutely tubereulated carinee, and 



