117 



transversed longitudinally by a mesial furrow ; the escutcheon is 

 depressed, lengthened, and narrow, its superior border is some- 

 what raised ; the costated portion of the shell has a numerous 

 series of about twenty oblique rows of tuberculated costae, of 

 which the first four or five are slightly curved and sub -tuber- 

 culated ; the tubercles are small, separate, rounded, regular, and 

 nearly of equal size. 



Obs. T. signata appears to be limited to the Inferior Oolite ; 

 Dr. Lycett says, "It appears to be present in Dorsetshire, judg- 

 ing from the matrix of two specimens which have come under 

 my notice." He does not, however, give the exact locality. 



TJRIGONIA IBKEGULAEIS, Seelach, plate ii., fig. 3. 



MONO. BEIT. Foss., TBIGONLE, Lye., Pal. Soc., p. 39, plate v., figs. 1, a.b, 

 2, plate vii., fig. 6. 



Damon Geo. of Weymouth, Sup., plate ii., fig. 3, 1880. 



Shell ovately trigonal, or oblong ; urnbones antero-mesial, 

 prominent, and recurved, anterior side -short, moderately convex, 

 slightly truncated, its lower portion curved, with the lengthened 

 lower border; the escutcheon is very large and depressed; its length 

 exceeding half of that of the entire shell, its superior border is 

 only slightly raised ; the area is narrow, having three tuber- 

 culated carinae, the inner and median carinae have each a row of 

 small transverse, nodose varices, rather distantly arranged; the 

 other portion of the valve has about fourteen rows of slightly 

 elevated costae, with distinct, conical, pointed, and unequal 

 tubercles, the first-formed six or seven rows are regular and con- 

 centric, those which succeed are more or less irregular, both in 

 their direction and the size and arrangement of the tubercles, 

 the anteal portion of the rows becoming broken and irregular. 



The figure in Mr. Damon's "Supplement" is an extreme 

 example of that general irregularity of the tubercles which 

 Seebach has adopted as a name for the species. 



Obs. It is moderately abundant in the Oxford clay, in the. 

 neighbourhood of Weymouth. 



