anatomy and life history of mollusca. 185 



Explanation of Plates. 



Plate iii., fig. 1. — Enlarged figure of Patella tramoserica, Martyn, 

 magnified about eight diameters. The eyes are represented on 

 three of the ribs only, but the sketch is an ideal one. On the 

 whole the eyes are not so uniform in size or so closely placed as 

 they are represented at the base of the central rib. 



Plate iii., fig. 2. — Portion of Radula. of Patella tramoserica, 

 Martyn, magnified 50 diameters. The teeth are in pairs with a 

 strong angular projection on the outer side. They are bent down 

 near the point of attachment to the chitinous membrane of the 

 Radula. These teeth are hollow and of dark brown colour. No 

 distinction in the form of the teeth seems to exist among a great 

 many species of Patella. 



Plate iv., fig. 3. — Radula of Acmcea septiformis, Q. & G. — In 

 this case the plan of the Radula which is similar to that of Patella 

 consists of teeth like Patella in alternate pairs, two or four in the 

 middle and one or two at each side. It is not nearly so long as in 

 Patella, being very little longer than the animal, and the teeth 

 are small. In the figure the teeth are not so well seen owing to 

 the partial investiture of the tube in which they are all sheathed. 

 It is not curved to the same extent in the animal. The portion 

 represented is opposite to the buccal end, and the teeth are in 

 ■consequence more glassy and transparent. 



Plate iv., fig. 4. — Portion of Radula of Cerithium ebeninum, 

 Bruguiere. The type of this Radula is that of a Siphonostomata 

 of the order Pectinibranchiata, sub-order Taenioglossa, group 

 Rostrifera. The teeth are few in number with a short Radula 

 having a broad central tooth overlaid with a number of sickle-like 

 lateral teeth. 



Plate v., fig. 5. — Back and front view of Cerithium ebeninum 

 Brug. 



Plate v., fig. 6. — Tentacle eye of Cerithium ebeninum, Brug., 

 showing two small subsidiary eyes on the choroid coat, and one on 

 the cornea, a and b choroid eyes, c eye on cornea. 



Plate vi., fig. 7. — Another tentacle eye of Cerithium or Triton, 

 genus uncertain, with facetted structure. 



Plate vi., fig. 8. — Shell-eye of Patella tramoserica, Martyn. 

 From the edge of the peristome obtained in a section of the shell, 

 a optic neve, b branch proceeding to upper portion of eye, c choroid 

 coat, d retina, tapetum and rods. 



Plate vii., fig. 9. — Portion of the dorsal mantle of Onchidium 

 ddmelii, showing cells containing partially formed shelly matter, 

 a fragments of carbonate of lime in cells, x 75 diam. 



