VoL 62.'] LIASSIC DENTALIIDJE. 589 



liemarks. — Only one example of this species, which is well- 

 defined, has passed through my hands. 



Dentalium subtrigonale, sp. nov. (PL XLV, figs. 2 a-2 d.) 



T.f. PI. XLV, figs. 2 a-2 d. 

 T.l. Folly-Lane clay -pit, Cheltenham. 

 DZ. Pliensbachian. 

 //. armati. 

 Colin. L. Kichardson. 



Syn. 1904. Dentalium aff. limatulum, Richardson, 'Handbook to the Geology of 

 Cheltenham ' p. 219, but not pi. xv, fig. 2. 



Diagnosis. — Shell small, thick (for its size) ; transverse section 

 subtriangular exteriorly, circular to subobvate interiorly ; dorsal 

 sides convex, but becoming flattened to convex towards the anterior 

 end in senile specimens. Sides subconvex anteriorly (especially in 

 senile forms, as in PI. XLV, fig. 2 c) ; but fiat posteriorly, where 

 they usually converge regularly until within a short distance of the 

 ventral side, when they are directed vertically to meet that side at 

 right angles, thereby giving rise to a prominent carina ; the 

 surface-ornamentation consists of fine, oblique, transverse lineae. 



He marks. — Dentalium subtrigonale presents three different out- 

 lines in transverse section. The majority of the specimens found 

 at the Polly-Lane clay-pit, when cut transversely anywhere in the 

 posterior half, present the outline shown in PL XLY, fig. 26; a 

 few when cut anywhere in the anterior half, a more or less trian- 

 gular section ; while others (chiefly mature forms) have only a faint 

 blunt ventral margin at or near the anterior extremity, and slightly- 

 convex lateral and dorsal surfaces (fig. 2 c). Some very mature 

 forms give an ovate transverse section of the anterior end, and have 

 a relatively-thick test with more conspicuous lineas. 



Dentalitjii Terqtjemi (Tate MS.), sp. nov. 



T.f. None. 

 T.l. Aiglemont. 



H. ' Assise a A. angulatus.' [Hettaugian.] 

 rj. [marmoreceZ] 



Colin. . 



Syn. 1865. Dentalium giganteum, Terquem & Piette, pars (non Phillips), 'Le 

 Lias Inferieur de l'Est de la France ' Mem. Soc. Geol. France, ser. 2 

 vol. viii, pp. 67-68. 



Diagnosis. — Shell ornamented with numerous, very fine, 

 closely-set linere. Diameter of transverse section = at least 2 milli- 

 metres. 



E em arks. — Concerning the forms which Terquem & Piette re- 

 ferred to Phillips's species, these authors remarked (translation): — 



' We refer to this species some fragments from 8 to 10 millimetres in length 

 by 2 in breadth, and ornamented wilh numerous very fine and closely-set 

 stria? ; the specimens which we possess from the Middle Lias of the Moselle, 

 Plicatula-spinosa zone, are more perfect, have a diameter of 5 millimetres for 

 a length of 50, and present the same ornamentation. 



' Locality : Zone of A. angulatus of Aiglemont.' 



In Ealph Tate's manuscript note-book, which Avas very kindly 



