E. S. Cobbold — Cambrian Hyolithidce from Hartsliill. 157 



Horizon and Locality . — Lower Cambrian : the red sandy limestone 

 of Woodlands Quarry, Hartshill. 



I desire to express my gratitude to Mr. L. J. Wills for allowing 

 me to study and describe bis specimens, and also to Dr. F. A. Bather 

 for much kind help in reference to the literature of the genera 

 Salterella, Stenotheca, and Helcionella. 



EXPLANATION OF PLATE IV. 



Note. —The numbers in square brackets are those attached to the blocks on 

 which the specimens are found. All belong to the collection of the Birmingham 

 University. 



Hyolithus (OrthotJieca) de Geeri, Holm, x 2. (See p. 150.) 

 Fig. 



1 [37]. Ventral side ; a, exterior ; b, section. 



2 [36]. Dorsal side, showing transverse lip ; a, internal cast; b, section. 



3 [34]. Ventral side, showing transverse lip ; a, external cast ; b, section. 



4 [29]. A detached internal cast ; a, dorsal; b, ventral; with sections at ends. 



5 [31]. Fragment showing sculpture ; a, ventral side ; b, section. 



6 [20]. An internal cast, showing form of septum. 



7 [12]. Interior of operculum "| 



8 [14]. External cast of operculum [-referred with reserve to this species. 



9 [18]. Internal cast of operculum 7 



Hyolithus biconvexus, sp. nov. x 2. (See p. 152.) 

 10. Type-specimen [31] ; a, exterior of dorsal side, with b, enlargements to 

 4 diameters to show character of sculpture. 



11 [36]. Fragment of exterior of ventral side. 



12 [34]. Internal cast ; a, dorsal side ; b, section. 



Hyolithus alatus, sp. nov. x 2. (Seep. 151.) 

 13. Type-specimen [34] ; «, dorsal side exterior ; b, side view ; c, section. 



14 [37]. Ventral side, showing lip slightly notched, with section. 



15 [33]. Internal cast, side view. 



16 [14]. a, internal cast of operculum referred with reserve to this species ; 



b and c, side and axial views in outline. 



Hyolithus Willsi, sp. nov. Nat. size. (See p. 152.) 

 17. Type-specimen [27 and 28]. An exfoliated dorsal side with form of shell 



shown by the weathered ventral side. 

 IS. Same specimen, side view in outline, reconstructed. 

 19, 20. Same specimen, diagonal sections at fractures XX and YY. 



Hyolithus cequilateralis, sp. nov. x 2. (See p. 153.) 



21. Type-specimen [2]. «, exterior ventral side and interior dorsal side ; 



b, section. 



22. Co-type [25]. Internal casts of two invaginated shells ; a, ventral side ; 



b, dorsal. 



Salterella (?) cf. S. curvata, S. & F. x 4. (See p. 154.) 



23 [38]. Exterior. 



24 [38]. Internal cast of a second specimen. 



Micromitra cf. Phillipsi, Holl, sp. X 5. (See p. 154.) 



25 [37]. External cast, with side view of a squeeze. 



Helcionella (?) emarginata, sp. nov. x 3. (See p. 155.) 



26. Type-specimen [46]. An internal cast, a, summit view; 6, side view; 



c, anterior view. 



27. Co-type [46]. a, internal cast of a second specimen, side view; 6, frag- 



ment of the external cast showing character of sculpture. 



