F. R. Cowper Reed — 8alters Undescribed Speciea. 125 



Measurements. mm. mm. 



Length 25 37 + 



Width at aperture ... ... ... ... 5 ? 



Eemakks. — Hyolithes Homfrayi is closely allied to H. bijugosus 

 (Salter) ^ from the Tremadoc beds. The apical augle, longitudinal 

 keels, and prominent mouth are similar ; but the stronger transverse 

 strise and the approximation of the lateral keels to the margin in 

 H. Homfrayi are points of difference. It may be compared with 

 the Swedish species H. pennatulus and H. triumvir^- but the material 

 is so poor that this species of Salter's cannot be held to rest on 

 a vei'y firm basis. 



Hyolithes sulcatus, Salter. (PI. VI, Fig. 4.) 



1873. T/ieca sulcata, Salter, n.sp. : Cat. Camb. Sil. Fosf3. Woodw. Mus., p. 17 



{h 322). 

 1891. Hyolithes .mlcatns, "Woods: Cat. Type Foss. "Woodw. Mus., p. 121. 



The two original specimens, h 322, which come from the base 

 of the Upper Tremadoc of Llanerch, west of Portmadoc, and were 

 presented by Mr. D. Homfray, consist of an internal cast and the 

 impression of the same. Since the aperture is more or less broken 

 and imperfect it is not possible to decide if it is the dorsal face 

 of the shell, but I am inclined to think it is for reasons which are 

 given below. Salter describes this species as " broad and short with 

 longitudinal folds." 



Diagnosis. — Shell conical, broad, short ; apical angle nearly SO'^, 

 trilobed, being divided into three elevated longitudinal ridges of 

 approximately equal size by two sharply impressed angular grooves. 

 The median ridge is rounded and convex ; the lateral ones are 

 angulated sharply down their centre. There are indications of 

 several (four or five) small, rounded, longitudinal I'ibs running down 

 the median ridge, and one or two less distinct ones on each of the 

 lateral ridges. No transverse striation is present. 



Measurements. mm. 



Length 23 



Breadth at front end 10 



Remarks. — In Hyolithes bijugosus (Salter) the convex side (which 

 is called by Salter in this species the dorsal) is described as ridged 

 with three distinct keels, the central one of which is the strongest, 

 but the small apical angle (10°-12°) and the transverse lines of 

 growth and absence of longitudinal ribs distinguish this species, 



Hyolithes Billingsi,^ from the Cambrian of Pioche, Nevada, resembles 

 M. sulcatus more closely in having an apical angle of nearly the 

 same size and the flattened dorsal side ornamented with three 

 longitudinal ridges divided by furrows. The longitudinal ribs 

 figured by Holm * in many Swedish species are found on the convex 

 ventral side, but in those forms (H. pennatulus, H. triumvir, etc.) 

 in which the edges of the dorsal face are folded round to the ventral 



1 Mem. Geol. Surv., vol. iii, 2nd ed. (1881), p. 559, pi. x, figs. 19, 20. 

 " Holm: Sver. Kamb. Sil. Hyol. o. Conul. (1893), t. iii, figs. 1-5, 6-11, etc. 

 s Walcott : " Fauna of the Olenellus Zone" (1890), p. 620, pi. Ixxt, figs. 1, la-c. 

 * Holm : Sver. Kamb. Silur. Hyol. o. Conul. (1893j, t. iii, tigs. 1-5, 6-11, etc. 



