174 INFERIOR OOLITE AMMONITES. 



1874. Ammonites steiatultts, Bumortier. Etudes pal. Bassin Ehone, 4e partie, 



pi. xvi, fig. 1, p. 64. 

 1876. Haepocebas steiatxtlum, Blake. Cephalopoda, Yorkshire Lias, p. 308. 

 1885. — — Haug. Beitr. Monogr. Harpoceraa ; Neues Jahr- 



buch fiir Mineralogie, &c., Beil.-Bd. 

 iii, p. 611 (pars). 

 1885. Ammonites eadians depresstts, Quenstedt. Amm. Scliwiibischen Jura, 



pi. li, fig. 13 only. 

 1887. — (Haepocebas) steiatplum, Denckmann. Fauna ober Lias 



Doernten ; Abh. geol. Specialkarte Preussen 

 und den thiiringischen Staaten, pi. viii, 

 figs. 2, 3 ; pi. X, fig. 12. 



Discoidal, compressed, subcarinate. Whorls elliptical, ornamented with fine 

 ventrally-projected subarcuate radii, which are sometimes more or less obsolete 

 upon the inner area. Ventral area not defined, carina small and barely distinct — 

 in the adult almost obsolete. No inner margin. Inclusion about one third. 

 Suture-line (PI. A, fig. 43) much the same as in Gramm. toarcense ; lobes very 

 shallow. Termination in youth with a small lateral, apparently spathulate, auricle 

 (PL XXVIII, figs. 20—21). 



Sowerby thus describes his species : " Discoid, carinated, radiated ; sides of the 

 whorl convex, the inner whorls exposed ; radii numerous, slender, undulated ; 

 surface covered with minute strise parallel to the radii ; aperture elliptical." 



I have caused to be redrawn the British Museum specimen (marked with the 

 green ticket used to indicate the figured type-fossils). It is possible that it may 

 have been broken and mended after it was figured in the ' Mineral Conchology.' 

 The broken portions have not been depicted by Sowerby ; and the pieces of shell 

 so sharply defined in his figure are not visible on this specimen. 



If it be not the original of the species yet I think that the specimen may 

 be considered typical ; and from it we see that the characteristics are fine, rather 

 obscure ribs — ^smaller than Sowerby's drawing might lead us to suppose — and 

 a very slender carina ; while the sides of the whorl are convex and slope gradually 

 towards both edges. 



The name " striatulus " was given to the specimen on account of the fine strias 

 observable between the ribs on the test. This feature, which is not confined 

 by any means to this species, is to be seen in well-preserved specimens only. 



This species may be regarded as inheriting the senile stage of Gramm. 

 toarcense very early, and continuing the features of that stage in the same line ; 

 and its relationship to toarcense has been discussed under that heading. To that 

 species some specimens show a reversion, in the production of coarse ribs late 

 in life. 



The horizon — a part of the Jurense-zone — of which this species and Gramm. 



