45 



mented by elevated longitudinal lines, of which about six- 

 teen may be counted near the smaller end, though they in- 

 crease in number by implantation, and diminish in size, 

 towards the lapger extremity ; lines of growth obscure and 

 passing rather oqliquely round the shell. 



Diameter near the smaller end *05 inch, and increasing to 

 •10 inch in a length of *50 inches. 



This species is nearly related to D. fragilis (Meek & Hay- 

 den, Proceed. Acad. Nat. Sci. PhiPa, vol. 8, p. 69), but dif- 

 fers in being much less strongly marked by the lines of 

 growth. It is also near D. gracilis (Hall & Meek, Memoirs 

 Am. Acad. Sci. and Arts, Boston, vol. 5, p. 393, fig. 11, a-c 

 pi. 3), from which it may be distinguished by its thinner 

 snell and more slender form, as well as by its less distinct 

 lines of growth. 



Ammonites (Scaphites?) ramosus. — General form oval dis- 

 coidal, much compressed, rounded on the dorsum ; umbili- 

 cus very small ; volutions increasing rapidly in breadth, and 

 more gradually in thickness, compressed on the sides; inner 

 ones almost entirely hidden. Surface ornamented by numer- 

 ous regular simple elevated transverse lines, which increase 

 in size with the volutions, and in crossing from the umbili- 

 cus, first curve obliquely forward, then gracefully a little 

 backwards, and on approaching the periphery again bend 

 slightly forward. 



Septa composed often lobes on each side, which diminish 

 regularly in size towards the umbilicus ; larger ones ex- 

 tremely complicated in their structure. Dorsal lobe about 

 one-third as large as the superior lateral lobe, having on 

 each side three main branches, of which the two at the ex- 

 tremity are larger than the others, and each again divided 

 nearly to the base, into two unequal slender parts the two 

 lateral of which have about four, and the two terminal two 

 principal branchlets,with many smaller sinuosities. Dorsal 

 saddle a little larger than the dorsal lobe, very oblique at 



[Trans, iv.] 8 



