126 F. R. Coirper Heed — Salter's Undescribed Species. 



side the trilobation of the ventral face is very marked. The 

 transverse striation is, however, a feature in these forms. The 

 material at our disposal is not sufficiently well preserved to decide 

 if S. siilcatus belongs to this latter group, called by Holm (op. cit., 

 p. 154) Magnidorsati, subgroup Garinati, and it is even impossible 

 to say positively if our specimens exhibit the dorsal or ventral face 

 of the shell, though I am inclined from the resemblance to 

 S'. bijugosus and M. Billingsi to consider it to be the dorsal. 



Hyolithes tkilineattjs, Salter. (PI. VI, Fig. 5.) 

 1873. Theea trilineata, Salter MSS. : Cat. Camb. Sil. Foss. Woodw. Mus., p. 18 



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



Salter describes this form as "a small species with "longitudinal 

 lines." The original specimen comes from the base of the Upper 

 Tremadoc, Moel-y-Gest, and was presented by Mr. D. Homfray. 

 It is not in a very good state of preservation, and shows only the 

 inner side of the dorsal face, but there are several other specimens 

 from the Tremadoc beds of Tyn-y-llan, Portmadoc, which show the 

 characters more distinctly. 



Diagnosis. — Shell conical. Apical angle 15°. Dorsal face 

 provided with strong median longitudinal carina for two-thirds 

 of its length from pointed apex. Anterior third of dorsal face 

 flattened with prominent semicircular lip ; carina obsolete on this 

 portion of shell. Carina bordered by a sharp deep groove on each 

 side which likewise die out in front. Between these grooves and 

 the lateral edges of the dorsal face are faint indications of longi- 

 tudinal ribs. On the anterior, flattened third of the shell two weak 

 indistinct ribs may be distinguished, apparently not continued 

 posteriorly towards the apex. 



Faint transverse striae, arched forwards, are present. (These are 

 best shown on some of the Tyn-y-llan specimens in which the shell 

 is preserved, but are visible also in the type-specimen.) 



Measurements; mm. 



Length 16 



Widtli at mouth 6 



Eemauks. — This species resembles H. aratus (Salter) ' from the 

 Lower (and Upper ?) Tremadoc in the raised keel along the dorsal 

 surface, the transverse arched strias, and size of the apical angle, but 

 differs in the reduction of the length of the keel and flattening of 

 anterior portion. 



EXPLANATION OF PLATE VI. 

 Fig. 1. Conularia clavus. x 2\. 



la. Ditto, showing groove at angle, x 2^. 



\b. Ditto, mouth, x 2|. 



\c. Ditto, ornamentation, x 10. 



2. Conularia hifasciata. Nat. size. 

 2a. Ditto, x 30. 



3. Hyolithes Homfrayi. x 2. 



4. H. sulcatiis. X 2. 



5. H. trilineatus. x 2. 



1 Mem. Geol. Surv., vol. iii, 2nd ed. (1881), p. 559, pi. x, figs. 15, 21. 



