GRAMMOCERAS SUBSERRODENS. 179 



nearly allied to Gramm. mactra than is really the case. As if to give further 

 strength to this idea, we have Gramm. suhserrodens (see below), also a finely- 

 ribbed species, in the same bed, and this species is, in outward shape, exactly 

 intermediate between Gramm. mactra and Lioc. opalinum. 



The head-quarters of Gramm. mactra are, in Grloucestershire, on the flanks of 

 the so-called Frocester Hill, namely, in Buckholt Wood and at Coaley Peak ; it 

 also occurs at Haresfield Hill. In Dorset it occurs in the Sand-rock of the Yeovil 

 Sands at Bradford Abbas ; but there it is very rare, and is with difficulty distin- 

 guished from its companion, the commoner Dumortlerla Moorei. 



Plate XXXI, fig. 1, represents the side view of a broken specimen of the 

 form a, with its fascicled strias producing bulgings or " false ribs " upon the inner 

 area ; fig. 2 shows its suture-line. On the same plate, figs. 3, 4 exhibit two views 

 of the senile form /3 ; fig, 4 is noticeable for its almost uncarinate ventral area. 

 Both these specimens came from Frocester Hill (Coaley Peak) OpaUnum-zone. 

 In Plate XXX, fig. 3, is seen the side view of the form y, noticeable for its well- 

 marked inner margin (the artist has somewhat exaggerated the irregular ribs) ; 

 fig. 4 shows the front view of this compressed form. Figs. 5, 6 illustrate two 

 views of the coarse-ribbed variety ^ ; and fig. 7 shows its suture-line. Of the two 

 specimens figured in this plate the first is from Buckholt Wood and the other 

 from Coaley Peak, two localities not very far apart. 



Grammoceras subserrodens { Branca). Plate XXXI, figs. 5 — 14. 



1879. Amaltheus subsebbodens, Branco. TJntere Dogger; Abhandl. z. geol. 



Spez.-Karte v. Elsass-Lothringen. 

 Bd. ii, pi. iii, fig. 2. 



Discoidal, compressed, carinate, in general form like a Lioceras. Whorls broad 

 and flattened, ornamented with fine, ventrally projected, subsigmoidal radii. 

 Ventral area undefined, the two sides sloping acutely, and forming a fairly pro- 

 minent carina. Inner margin distinct, upright or slightly concave. Inclusion 

 one-half to two-thirds. Umbilicus small but shallow. Suture-line simple, little 

 ornamented, superior-lateral lobe but little longer than siphonal, inferior lateral 

 about half the size, three or four small denticulations representing incipient 

 auxiliaries. 



Branco considered his species to belong to the genus Amaltheus, that is to say, 

 to the group of Am. serrodens, which has often been placed in that genus. He 

 supposed that the species was closely related to his "Amaltheus" Fridericii; but 



