140 SOME NEW SPECIES OF AMMONITES. 



Amaltheus subspinatus, S. S. Buck., plate ii., figs. 1 a-b-c. 



1881. Amaltheus SUBSPINATUS, S. S. £uck., 2 Journal Geological Society, 

 vol. 37, p. G06. 



Whorls numerous, increasing in breadth very slowly ; inclu- 

 sion, barely any ; ornamentation, rather large angular ribs pro- 

 duced forward on the ventral area, then gradually diminishing 

 in size and passing across the keel to join the one on the other 

 side. Between these are numerous very fine lines. On each rib 

 are two smallish spines, one on the outer the other on the inner 

 part of the whorl ; keel distinct and crenulated ; aperture 

 quadrangular ; mouth-border plain bend produced on the ventral 

 area ; body-chamber one-half whorl in length. 



It will at once be observed the great difference between this 

 species, and the last in every respect easily leading one to 

 suppose that they could hardly belong to the same genus. This 

 species, however, is closely allied to Amaltheus spinatus (Brugiere) 

 of the Middle Lias, which is more or less connected by its 

 crenulated keel, &c., to the type of the genus Amaltheus 

 margaritatus (Montfort), which type is connected, so to speak, 

 through Amaltheus Enqelharti, Amal. oxytiotus, SfC, to Amal. 

 Stephani, ^c. I will, however, leave the question of genera to 

 those who have opportunities of studying Ammonites from all the 

 various formations, merely remarking that the addition of new 

 forms will be a great help and probably enable new genera to 

 be separated and well defined. Amaltheus subspinatus is a some- 

 what frequent fossil, but I believe very local. 



Localities, quarries near Bradford Abbas and near Half-way 

 House, Dorset. 



Position, zone of Harpoceras Sowerbyi. 



Nearest Allied Form. — Amaltheus spinatus, but our species has 

 more ribs, less inclusion, and two rows of spines. 



The figure represents a full-grown specimen, natm-al size. 

 Figure Ic is to show the mouth-border. 



