PLATE II. 

 Figures la-lm. — Leptochiton benthus, n. sp. 



Figure la. — Upper surface of first two valves x 6 diam. 

 lb. — Lower surface of first two valves x 6 diam. 

 lc. — Upper surface of last two valves x 6 diam. 

 Id. — Lower surface of last two valves x 6 diam. 

 le. — Side view of first two valves x 12 diam. 

 1/ — Side view of last two valves x 12 diam. 

 lg. — Portion of jugum of an intermediate valve, magnified. 

 \h. — Upper portion of a lateral area of the same, maguified. 

 \j. ■ — Portion of a pleuron of the same x 26 diam. 

 Yk. — End view of an intermediate valve x 5 diam. 

 11. — Under surface of entire animal x 61- diam. 

 \m. — Terminal portion of same x 8 diam. 



Figures 2a-2d. — Leptochiton belknapi, Dall. 



Figure 2a. —Side view of whole animal x 6 diam. 



,, 2b. — End view of an intermediate valve x 6 diam. 



„ 2c. — Portion of a pleuron of an intermediate valve x 26 diam. 



„ 2c?. — Spicules of the girdle, greatly magnified. 



Figures 3a-3e. — Leptochiton kerguelensis, u. sp. 



Figure 3a. — Upper surface of anterior valve x 18 diam. 

 „ 3b. — Upper surface of intermediate valve x 18 diam. 

 „ 3c. — Upper surface of posterior valve x 18 diam. 

 „ 3d. — End view of an intermediate valve x 10 diam. 

 „ 3e. — Diagram of under surface of whole animal x 4 diam. 



Figures 4a-4Z. — Hemiarthrum setulosum, Carp. 



Figure 4a. — Upper surface of first two valves x 71 diam., i. pi., insertion plate. 



„ 4b. — Under surface of first two valves x7| diam. 



„ 4c. — Upper surface of intermediate valve x 7£ diam. 



„ id. — Under surface of intermediate valve x 71 diam. 



,, 4e. — Upper surface of posterior valve x 71 diam. 



„ 4/. — Under surface of posterior valve x 7 J diam., *'. pi., insertion plate. 



,, 4g. — End view of an intermediate valve x 71 diam. 



„ 4h. — Side view of central portion of animal x 1\ diam. 



,, ij. — Diagraniatic transverse section of animal x 4 diam. 



,, 4k. — Under surface of whole animal x 3| diam. 



,, 41. — Terminal portion of same x 6 diam. 



