Ill 
AMMONITES Henslowi. 
TAB. CCLXII. 
Sp. Char. Discoid ; sides flat ; front rounded ; 
inner whorles exposed ; septa, with three 
entire tongue -formed sinuses upon each side ; 
aperture obovate. 
AlBout 12 septa, with margins that are remarkably en- 
tire for an Ammonite, occupy each whorle of this curious 
Shell ; the three sinuses on e&ch side the edges of the 
septa correspond in shape with the intermediate projec- 
tions which have, in the cast, the form of a to ngue, or 
the sole of a pointed shoe, being contracted towards their 
bases ; on the front of the edge is an acute sinus, which 
contains the siphuncle ; the whorles are about four; the 
length of the aperture is about two fifths the diameter of 
the shell and double the thickness. 
This is one of many curious petrifactions found by 
J. S. Henslow, Esq. during a visit to the Isle of Man 
in 1819; it is in the compact dark grey Limestone 
which occurs at Scarlet in that Island. The want of the 
minutely sinuated edges of the septa, is a character that 
several other Ammonites possess. The Woodwardian 
Professor at Cambridge has selected two foreign speci- 
mens which have the septa lobed, but unless the surfaces 
of the casts have been deeply worn, the lobes have entire 
edges : such species are not however numerous, and 
specimens of them are rare ; the foreign one I have 
made a 4to plate* of, for the sake nf comparison and 
named it Ammonites Sedgwicki in hpnour of the Profes- 
sor whose name I think it will be a pleasure to comme- 
morate. 
* I have also engraved several other foreign, unique, or remarkable 
Shells, which are sold separate. 
