SCAPHOIDE^. 17 



Trigonia conjungens, Phil., Pggaster semisulcatiis, Phil., and a considerable series of 

 Inferior Oolite Conchifera, some of the more common forms of which occur also in the 

 Dogger and in the Grey Limestone upon the same coast and vicinity. The position of 

 this marine deposit (from fifteen to twenty feet in thickness), about the middle of the 

 great mass of Estuarine Sandstones and Shales, and between the Dogger and the Grey 

 Limestone, is important as tending to connect the fauna of those two widely separated 

 marine deposits, and as proving that the conditions of sea-bottom and the succession of 

 molluscan life underwent no considerable change during the whole of the northern Inferior 

 Oolite period as exemplified upon the coast of Yorkshire, undoubtedly less than is 

 exhibited by beds of the same geological period at the southern localities. Two other 

 less important marine beds also occur intercalated with the estuary deposits, one between 

 the Dogger and the Millepore bed, the other between the latter deposit and the Grey 

 Limestone; but as their marine testacea are few and ill-preserved, little interest attaches 

 to their presence. 



Specimens of T. recticosta from Cloughtoh are in the collection of Mr. Leckenby at 

 Scarborough and in the cabinet of the author ; others in a less perfect condition are in 

 the Museum of the Yorkshire Philosophical Society at York. The British Museum has 

 also a fine specimen in the Bean Collection. 



Trigonia Bathonica, Lye. Plate I, fig. 3. 



Trigonia Bathonica, Lycett. Pal. Soc. Suppl. Monog., 1863, p. 52, pi. xl, fig. 3. 



Shell sub-trigonal, short, depressed ; umbones elevated, mesial and not recurved ; 

 anterior and posterior borders nearly straight, sloping obliquely downwards, the surface 

 with numerous (about twenty-four) narrow, elevated, spinose, somewhat undulated and 

 slightly radiating costae, which are directed from the marginal carina anteally down- 

 wards, and all reach the pallial margin ; the area is narrow and transversely striated j the 

 marginal carina is very small and rather indistinct. 



The narrow ridge-like costse are very closely arranged, and have numerous minute 

 obtuse spines, which impart roughness to the surface ; the general aspect resembles T. 

 duplicata, Sow., but it has no bifurcating or interstitial costse near to the lower border, 

 it is also without concentric costae near to the apex ; the absence of this latter feature 

 will also distinguish it from T. gemmata, Lye. The sole specimen at my disposal is 

 imperfect at the posterior extremity ; it has twenty costae, and would require about 

 four others to complete its surface. The figure is nearly an equilateral triangle, 

 each of the sides having a length of about an inch. 



Oppel, in his elaborate work ' Juraformation,' p. 486, makes incidental mention of a 

 Trigonia which is regarded by Messrs. Rigaux and Sauvage as identical with our species. 



3 



