48b YORKSHIRE TYPE AMMONITES Feb. 



4S. AMMONITES SIPHUN'CULARIS, Simpson 

 (Plate XI.VIII) 



Original Description 

 "87. A|mnionitesJ siphunculaiis. |M. Simpson, 1843, j). 4').] 



[" II. With a keel on the back." p. 31. 

 " b. Outer whorl narrower." \>. 44.] 



" De])ressed, volutions 4, exposed ; radii straight, strong, obtuse, 

 separated by narrow furrows ; siphuncle on the back equal to half the 

 breadth of the whorl ; diameter ,% inch. 



" This is a most singular species, the keel being formed of a very 

 distinct tube, which deeply indents the inner part of the succeeding 

 whorls ; if we neglect the keel, the aperture would be nearly round. 

 It is from the lower beds of lias at Robin Hood's Bay ; for the discovery 

 of this, as well as many other species, we are indebted to 1 homas Crosby, 

 a diligent collector of fossils, who has brought to light many large and 

 interesting species, and who has a quick eye in detecting small ones." 



Additional Details 



Simpson, 1855, 88, ends ist sentence of 2nd par. with " tube " ; 

 then proceeds instead of rest of par. " In one sj)ecimen, part of the tube 

 has been broken off, and the radii are seen to pass over the back, strongly 

 resembling those of A. maculatus. The cast is smooth and the shell 

 rough.— L.L., R.H. Bay." 



Simpson, 1884, 126, i)ractically the same. 



RciiKirks 



Stages, conch, serpenlicone ; ])eri])hery, I : ornanionl, 4. 

  Tlie tube which caused Simj)son to give the name is due to a Serpula. 



This is a jmmitive Capricorn, which, if it developed, may have given 

 rise to Androgynoceras or other genera of Lij)eroceratidK, or, perhaps, 

 to Echioccras. A generic name is uncertain. Therefore Androgynoceras ? 

 Hyatt, i8()7 ; family Liparoceratidte. The geological jwsition is pre- 

 sumably L.L. 15. 



RcsitU 



Andkogynocer.\s ? siPHLNCULARE, SiMPSON sp. iiS4J, Sincmuriau, 

 [oxynotmn zone ?], Robin Hood's Bay, near Whitby. 



