129 

 TRIGONIA TENUITEXTA, Lye., plate v., fig. 4. 



MONO. BEIT. Foss., TEIQONIJE, Lijc., Pal. Soc., p. 90, plate xx.,figs. 1, la. 

 Damon's Geology of Weymouth, Sup., plate xvi., 

 fig. 3, 1880. 



Shell with the general outline of T. Damoniana but less con- 

 vex ; its most striking peculiarity is the ante-carinal space, which 

 is nearly absent, there being only a narrow slight depression, 

 indicating its position ; the knotted costee upon the side of the 

 valve are remarkable for their minuteness, close arrangement, 

 and irregularity of undulations, so that they appear partially 

 confused. Of the specimens figured in his Monograph, I>r 

 Lycett says, "the escutcheon has a few irregular oblique plica- 

 tions ; as this is a feature altogether foreign to the Glabrce, and 

 occurs only in the Quadratce and the Costatce, its occurrence in the 

 present instance may be regarded as an abnormal or individual 

 peculiarity. 



Obs. T. tenuitexta is met with in the Limestones of the Isle 

 of Portland. 



TRIQONTA MAN.SELI, Lye., plate v. fig. 2. 



MONO. BEIT. Foss. TEIGK>NLE, Lye., Pal. Soc., p. 86, plate xix., figs. 3, 4, 

 4a > 6 - - 



Damon's Geology of Weymouth, Supp., pi. xiv., fig. 

 4, 1880. 



Shell subovate or ovately oblong, inflated mesially, compressed 

 near its pallia! border ; umbones antero-mesial, prominent, large, 

 and obtuse, much incurved and nearly erect ; anterior and lower 

 borders curved elliptically ; hinge-border rather convex, curved 

 gently with the posteal extremity of the area, and terminating 

 in an extremity which is somewhat produced and pointed; 

 escutcheon smooth and concave, having its upper border some- 

 what raised ; area narrow, convex and raised, divided con- 

 spicuously by a deep mesial furrow, which has bordering upon 

 it upon either side, a slightly defined row of small or evanescent 

 tubercles. The other portion of the surface has a very 

 numerous and well-marked series of obliquely directed tuber- 



