﻿DUMORTIERIA COSTULA. 237 



The only species which at all approach this are Bum. sparsicosta, Haug, and 

 Dum. costula (Reinecke). Both of them are doubtless its direct descendants. 

 The former differs in having considerably more compressed, broader, and more 

 ventrally-sharpened whorls, greater inclusion, and fewer turns in the umbilicus ; 

 while the latter differs very much in the same features, but has a more gibbous 

 ventral area than sparsicosta. 



The specimen figured is the only example known to me. It was collected by 

 Mr. Darell Stephens, F.G.S., &c, and, as is the case with his specimens, its 

 locality is accurately recorded. The label says, " The Sands, Hendford Hill, 

 Yeovil ;" and its horizon, therefore, is the lower part of the Yeovil Sands — in 

 other words, the Bumortieria-beds (Jurens e-zone). 



PI. XXXVII, figs. 9, 10, give two views of this specimen, and fig. 11 illustrates 

 the characteristic suture-line. 



Dumortieria costula (Reinecke). Plate XXXVII, figs. 12 — 15. 



1818. Nautilus costula, Reinecke. Maris protogsei, figs. 33, 34. 



1846. Ammonites eadians costula, Quenstedt. Ceph., pi. vii, fig. 11. 

 1858. aalensis costula, Quenstedt. Der Jura, pi. xl, fig. 11. 



1884. Habpocebas Munieei, Rang. Nouv. A mm. ; Bull. Soe. geol. France, 



3e serie, t. xii, pi. xiii, fig. 3. 



1885. — — — Beitr. Monogr. Harpoceras ; Neues Jahr- 



buch fiir Mineral., &c, Beil.-Bd. iii, 

 p. 663. 

 1885. Ammonites steiatulo-costatus, Quenstedt. Amm. Sckwabischen Jura, 



pi. Hi, fig. 8 only. 

 1885. — costula, Quenstedt. Ibid., pi. liv, figs. 10 — 14 only. 



1885. — falcofila-spaesicosta, Quenstedt. Ibid., pi. liv, fig. 35 only. 



1887. Dumoetieeia Munieei, Hmig. " Polymorphidae," Neues Jahrbuch fiir 



Mineralogie, &c, Bd. ii, p. 132. 

 Non Am. costula, Dumortier, Branco, Bayle, Vacek, &c. (see next page). 



Discoidal, compressed, carinate. Whorls elliptical in shape, with gibbons 

 sides, ornamented with distant, but not very prominent, unequally-spaced, direct, 

 ventrally -inclined ribs. Between the ribs are indications of faint radii upon the 

 core ; but on the test are very fine strise. Ventral area undefined, very slightly 

 carinate. No inner margin. Inclusion about one-third. 



The small specimen figured seems to me to agree with Reinecke's somewhat 

 dubious figure better than anything else I possess. The larger specimen appears 

 to differ from the smaller only in being somewhat less carinate ; and possibly its 

 whorl at the same size is a little more gibbous. This larger specimen, however, 



