122 



TRIGOXIA MURICATA, GoUf, plate iv., fig. 1. 



MONO. BEIT. Foss., TEIOONLS:, Lye., Pal. Soc., p. 50, plate ix., fig-. 1. 



The shell of this species has a lengthened oblong form, with 

 the anterior side very short, and the posterior attenuated ; the 

 anterior and lower borders are curved elliptically ; the umbones 

 have but little elevation, but are distinctly recurved; area large and 

 flattened, or slightly convex posteally, having tuberculated carinse, 

 the marginals bearing regularly rounded and rather distinctly- 

 arranged tubercles ; the lateral costse have only a slight 

 elevation ; they are numerous (about twenty-four), obliquely 

 curved, and nearly of equal size, the tubercles small, numerous, 

 regularly, and slightly compressed laterally ; the larger tubercles 

 occupy the middle and posteal portion of the rows. 



Obs. Several examples of this species have been met with in 

 the Portland beds of Dorsetshire ; but deprived of their tests' 

 and do not exhibit the character of the area. 



UNDULATJE. 



TRIGONIA CONJTJNGENS, Phil. 



MONO. BEIT. Foss., TEIGONLZB, Lye., Pal. Soc., p. 62, pi. x., figs. 5, 7, 8, 

 pi. xiii., fig. 6. 



Shell ovately oblong, moderately convex mesially, somewha 

 depressed near to the anterior and posterior borders ; umbones 

 elevated, obtuse, erect or slightly re-curved, 

 placed within (or in some specimens upon) 

 ^.he line of the anterior third of the valves 

 anterior border produced, curved ellipti- 

 cally with the lower border ; hinge-border 

 straight, lengthened, sloping obliquely 

 and terminating posteally in the wide- Trigonia conjungens, Phil 

 rounded posteal border of the area ; escutcheon large, lengthened, 

 depressed, excepting its superior border, which is raised ; area 

 very wide, occupying about one- third of the surface of the valve ; it 

 is somewhat raised, expanded and flattened posteally ; it has a 



