POSITIONS OF THE TKIGOXI.^ OF 2;0RTH OXFOEDSHIRE, ETC. 43 



costae are not only much thickened, but pass with slight interruption 

 and with strong undulation from the anterior edge of the shell over 

 the carina, where they are much enlarged, and across the area to 

 the posteal border. 



The species is related to Trlgonia undulata of Agassiz *, from 

 which it differs in the peculiar irregularity of its ornamentation. 



At Sharpshill quarry near Hook Norton I have found this 

 species in a bed of exceedingly hard siliceous limestone of the 

 Inferior Oolite crowded with T. signata and yielding also Ammonites 

 Parhinsoni. At Hook j^orton fragments occur in the same horizon. 

 The matrix at Sharpshill is so intractable that it is a matter of the 

 greatest difficulty to extract specimens. 



I have named the species Trigonia Lycettii as a slight tribute to 

 the memory of that veteran paloeontologist the late Dr. J. Lycett. 



T. Lycettii, var. corrtjgata. (PI. I. fig. 3.) 



The contour of this variety is similar to that of the previously 

 described form, fig. 1. The shell, however, is larger, the measure- 

 ment being 2| X 2| inches. The costse are finer and much more 

 numerous, about twenty-four, the first five or six only being 

 unbroken ; those succeeding them descend steeply from the anterior 

 margin, whilst the lowest set, in confused arrangement, curve 

 irregularly with the lower border. They are cord-like and knotted 

 at the anterior ]3art of the shell, passing into scattered tubercles 

 towards the middle (or vanishing), and then, thickening, ascend 

 steeply towards the carina in straight or slightly undulating 

 tuberculate or plain ridges. An ante-carinal furrow causes the 

 costse to wave before passing over the carina. Area concave, covered 

 by bold continuations of the costse, which are knotted slightly on the 

 carina and parted in the middle of the area by a depressed vertical 

 line. 



Locality smd position. — Inferior Oolite, Sharpshill, as before. 



Trigonia conjttngens, Phill. — Specimens from beds C, of Hook 

 Norton, and from the Clypeus-grit of Over Norton, seem to justify 

 its mention here, though I catalogue the species with considerable 

 doubt. It appears in Beesley's lists f of Hook-Norton fossils together 

 with T. Phillijpsii, Mor. and Lye, T. v-scripta &c. 



Trigokta duplicata, Sow., appears only as a badly preserved shell 

 inside a valve of T. signata. Its position is probably L), Hook Norton. 

 I have in my cabinet a fine example from the zone of Am. Parhinsoni 

 at Avoncliffe. Lycett quotes it from the Upper Trigonia-grit also. 



Teigonia gemmata. Lye. The figure in the left-hand corner of 

 pi. ii. of supp. no. 2 to the Brit. Trigoniae should both in text and 

 plate appear as no. 6, not no. 8. Both it and a pretty little varietal 

 form in my collection have been derived from the lower part of 



* Mem. sur les Trigonies, tab. x. fig. 14-16. 



t " On the Geology of the Eastern Portion of the Banbury and Cheltenham 

 Direct Hallway," by Thomas Beesley, F.C.S. Proc. Geol. Assoc, vol, v, p. 7. 



