124 F. R. Cowper Heed — Salter's Undescrihed Species. 



from the apex towards the apertural margin. Surface of shell 

 ornamented by very fine, closely placed transverse lines, gently 

 arched forwards parallel to the margin of the aperture, and closely 

 set with microscopically minute oval tubercles, longitudinally 

 elongated and arranged in regular longitudinal lines, giving a 

 shagreen-like appearance to the shell. This ornamentation is not 

 interrupted in the least in crossing the median ridge or the edges of 

 the septa. 



Measurements. 



Length ... ... ... ... ... ... ... 65 mm. 



Width of aperture 22 mm. 



Apical angle ... ... ... ... ... ... 20° 



Eemarks. — The two Swedish Silurian species which very closely 

 resemble C. bifasciata are C. bilineata (Lindstrom) and G. aspersa 

 (Lindstrom).' Both of these possess the thin shell, the curious pair 

 of septa in the middle of the face, and the same style of orna- 

 mentation. G. bilineata also shows traces of the small median ridge 

 between the septa. The ornamentation of G. aspersa appears to 

 resemble that of G. bifasciata most closely. But both the Swedish 

 species differ in their apical angle, being much larger, i.e. from 

 30° to 35° instead of 20°. It is noteworthy that the specimen of 

 C. bilineata described by Lindstrom (loc. cit.) is apparently 

 preserved in much the same way as our specimen of G. bifasciata, 

 for both have their extremely thin shell wrinkled and of a chestnut- 

 brown colour. 



Htolithes Homfrayi, Salter. (PI. VI, Fig. 3.) 



1873. TJieea Homfrayi, Salter : Cat. Camb. Sil. Foss. Woodw. Mus., p. 8 {b 263). 

 1891. mjolithes Homfrayi, Woods : Cat. Type Foss. Woodw. Mus., p. 120. 



This species is described by Salter (op. cit.) as "much longer 

 than Theca corrugata." There are several specimens of this form 

 in the Woodwardian Museum, one of the three original slabs 

 labelled b 263 showing several individuals. Unluckily none are 

 well preserved, and consequently the description of the species 

 cannot be quite satisfactory. They come from the Menevian beds 

 of Tyddyngwladis, and were presented by Mr. D. Homfray. 



Diagnosis. — Shell conical, elongated ; apical angle 10°-15°. 

 Face (ventral ?) shows one longitudinal, narrow median ridge 

 apparently accompanied by a slight infolding of the shell, with 

 a lateral ridge on each side of it close to the margin of the face, 

 apparently representing the inflexed margins of the dorsal face. 

 In one specimen strongly marked growth-lines, arched forwards, 

 cross the face between the lateral ridges, but outside these ridges 

 their direction slightly changes. Aperture prominent, arched 

 forwards. A distorted oval object near the mouth of the figured 

 specimen may represent the operculum. 



1 Lindstrom: Sil. Gastrop. Pterop. Gotl. (1884), pp. 45-47, pi. i, figs. 4-8; 

 pi. yii, figs. 1-3 ; pi. xix, fig. 1. Holm : Sver. Kamb. Sil. Hyol. o. Conul. (1893), 

 p. 134, t. vi, figs. 38-42, 43-46. 



