AMALTHEUS WILTSHIREI. 393 



convexity of tlie middle third, and the thinness and concavity of the outer tliird, whilst the 

 keel is sharp and cutting. The shell is thin, often preserved, and covered vi^ith fine striae. 



The lobe-line (fig. 5) is much more simple than the lobe-line of A77iaL oxynotus. The 

 siphonal lobe has a few short digitations. The siphonal saddle is oblique, with four or 

 five simple folioles. The principal lateral lobe is short and narrow, with a few lateral 

 digitations; the lateral saddle resembles the siphonal in its simple folioles ; the lateral 

 lobe is short and stunted, with a few digitations, and the whole structure appears to be 

 like a dwarfed imitation of the lobe-line of Amal. oxynotus. 



The morphology of this species is not well known. I have figured two small examples 

 from the same collection, which very much resemble young forms of Amal. oxynotus of about 

 a like diameter. Tt certainly very much resembles that Ammonite, and may prove to be 

 only a variety of that fine shell. The materials at my command, however, are so limited 

 that I cannot venture upon a decided opinion on the subject. 



Affinities and Differences. — The affinities all connect this shell with Amal. oxynotus, 

 but it differs from that Ammonite in having the inner third of the whorls inflated, the 

 sides without ribs, and a much simpler lobe-line. These characters, although shght, are 

 said to be constant, and are considered to afford proofs of its being really distinct. 



Locality and Stratiyraphical Position. — The type specimen was collected from the 

 Amal. oxynotus-zoriQ, Robin Hood's Bay. It does not appear to have been found, according 

 to Professor Blake, out of Yorkshire. 



Amaltheus Wiltshirei, Wriyht, nov. sp. PI. XLVIII, fig. 3. 



Diaynosis. — Shell discoidal, very much compressed, outer volution very large, enve- 

 loping all the inner whorls ; sides high, convex, and covered with slight sigmoidal folds, 

 best seen on the mould. Shell structure ornamented with very delicate lines, which 

 describe the curve seen on the mould ; umbilicus occluded by the outer whorl ; siphonal 

 area thin and narrow ; keel blunt. 



Dimensions. — Transverse diameter 125 millimetres; height of the outer whorl 70 

 millimetres ; width of aperture 24 millimetres. 



Description. — This Ammonite was collected several years ago from the Green 

 Ammonite Bed near Charmouth, and since that discovery a second specimen has come 

 into my possession, with some of the associated species embedded in the block. I have 

 examined all the collections of Lias fossils to which I have had access with a view to 

 identify the species, but invariably without success, and conclude the form is new and 

 rare. I have, therefore, very great pleasure in dedicating it to my old friend, our worthy 

 Secretary, the Rev. Professor Wiltshire, F.G.S., as a humble but sincere acknowledgment 

 of the great assistance he has given me in prosecuting this work. 



51 



