GRAMMOCERAS STRIATULUM. 175 



toarcense are together characteristic lies in Yorkshire above the Alum-shale with 

 Eild. hifrons and Dactyl, commune, and below the Grey Sands with Dumortieria 

 sp. Pelecoceras affine, Pel. Sinon (Bayle) — (see above, p. 167).^ 



Leaving Yorkshire, we do not find any record of this species or its horizon 

 until we reach the south side of the Stroud Valley.^ From thence to Wotton- 

 under-Edge it occupies an horizon just above the Cotteswold Sands (sections vi — 

 vii, p. 45, 46; section x, p. 164). 



At Little Sodbury it occurs in several rock-bands in yellow sands^ (section xi, 

 p. 164), and I have also found it in Sands at Hinton. 



At Lyncombe Cutting, on the Somerset-and-Dorset Railway between Bath 

 and Midford, I have found it beloiv yellow sands — the Midford Sands (section 

 xii, p. 165). A specimen from Trent, Somerset, and a fragment from White 

 Lackington, near Ilminster, referred to this species, are from the so-called 

 *' Upper Lias." 



It is interesting to notice that Gramm. striatulum and toarcense would, in 

 accordance with some geological divisions, have to be quoted as in the Lias in 

 Somerset, and in the Inferior- Oolite Series (" so-called Midford Sands ") in 

 Gloucestershire. It is needless to point out that the horizon is really the same in 

 both cases ; but the lithology is different, and correlation by lithological characters 

 has caused the error. The same remark applies to several other species, such as 

 Gramm. doerntense, Gramm. dispansuin, Amm. discoides, &c. 



On account of the same facts Dr. Wright, having divided these strata into 

 three horizons, called, in ascending order, the Upper-Lias Clay, the Upper-Lias 

 Sands, and the Upper-Lias Cephalopoda-bed, stated that certain species were 

 common to the three horizons. The explanation of this can be found at p. 167. 



The typical Gramm. striatulum does not occur so frequently as might be 

 supposed from its quotation ; but this is because its name has in general, as well 

 as in the earher parts of this Monograph, been used to include Gramm. toarcense 

 (p. 171). 



Plate XXVI, figs. 7, 8, give two views of what is believed to be Sowerby's 

 type-specimen of Ammonites striatulus, which is contained in the British Museum 

 Collection and came from Robin Hood's Bay, Yorkshire; fig. 9 is added to show 

 the curvature of the ribs accurately, a feature so characteristic of Grammoceras, 

 and it is taken from a rubbing of the surface; fig. 10 is the suture-line of this 



1 From examination of 8i)ecimens sent by Mr. Hudleston. See also his paper on " The 

 Yorkshire Oolites," ' Proc. Geologists' Assoc.,' vol. iii, No. 7, pp. 294, ef seq., 1874 ; and Tate and Blake, 

 ' Yorkshire Lias,' pp. 181, 191, 1876. 



^ P. 45, bed 19. The fragments referred to Gramm. striatulum at Haresfield Hill do not belong 

 to that species or to Oramm. toarcense. 



^ "When I wrote p. 49 I did not know that the sands also occurred above Gramm. striatulum. 



