SYKES : BRITISH CHITONS. 



37 



The following key may help to distinguish the species : — 



Insertion-plates : none. 

 Lepidopleurus cancellatus, lateral areas raised. 



onyx, ,, ,, not raised. 



scahridus, foot claret-colour. 



Insertion -plates in head valve only and uusUt. 



JSanleya Ranlciji. 



Insertion-plates in all valves and slit. 



girdle smooth. 



,, nearly smooth. 



,, diamond-patterned and plates connected across 

 the sinus, 

 girdle scaly and gills nearly to head. 

 ,, ,, mecUan. 

 Acanthochites fascicularis, ,, with tufts of spines, granules on shell oval. 

 discrepans, ,, ,, ,, ,, round. 



Totiicella marmorea, 



ruber, 



Callochitou l<evis, 



TrachydcrmoH cinereus, 

 albus. 



EXPLANATION OF PLATE III. 



a, anterior or head valve ; b, central or median valve ; c, posterior or tail valve. 



Fig. 1. — Hanleya Hanleyi. 



2. — Lepidopleurus onyx. 



3. — Lepidopleurus cancellatus. 



4. — Lepidopleurus scabridus. 



5. — Acanthochites fascicularis. 



6. — Acanthochites discrepans. 



7. — Lepidopleurus scabridus. 



8. — Callochiton laevis. 



9. — Tonicella marmorea. 

 10. — Trachydermon albus. 

 11. — Trachydermon cinereus. 

 12. — Tonicella ruber. 



