42 



As the only specimen of this species in the collection is 

 much distorted, and not in a condition to show its finer sur- 

 face markings, if there were any, it may hereafter be found 

 necessary to modify somewhat the above descriptioD. 



Ph^ladomya subelongata. — Shell elongated, depressed, 

 gibbous down the oblique umbonial slopes ; beaks nearly ter- 

 minal, somewhat elevated, incurved, apparently touching ; 

 buccal end rounding up abruptly from below, slightly gap- 

 ing ; anal extremity rounded or subtruncate ; cardinal bor- 

 der depressed and nearly straight behind the beaks ; base 

 closed, slightly convex, nearly parallel with the dorsal edge. 

 Surface ornamented by about sixteen slender, slightly ele- 

 vated, radiating costee, most of which pass from the beaks 

 obliquely backwards to the base ; on the anterior end, and 

 dorsal region, they are much less distinct, and more widely 

 separated than on the middle of the shell ; very small indis- 

 tinct concentric wrinkles mark the surface in the other di- 

 rection, giving the costas a faint, irregular, nodose or granu- 

 lar appearance. 



Length 1*80 inches ; height '93 inch ; breadth *85 inch. 



The only specimens of this species in the collection have 

 suffered some distortion from pressure, and are not in a con- 

 dition to have preserved fine lines of growth, or other deli- 

 cate surface markings if they ever existed. The most 

 marked characteristics of the species are its elongated ver- 

 tically compressed form, nearly terminal beaks, and rather 

 sharp, slightly elevated, obscurely nodose costa?. 



In form it is much like the elongated varieties of an Ooli- 

 tic species described by Prof. Agassiz under the name of 

 P. foliacea (See Etudes critiques, Sur les Mol., Fos. T. 7. f. 

 fig. 4-12), but the beaks are more elevated, less oblique and 

 not quite so nearly terminal. The radiating costse are also 

 more numerous, and the concentric wrinkles not so strong 

 and regular on our shell. 



Trigonia Evansana.— Shell trigonal, very gibbous in front, 



