\S4 SYSTEMATIC ARRANGEMENT 



f Margin bristly ; lateral area of valves distinct. 



1 . M. nobilis. New Zealand. 



ft Margin spinose or spinulose ; lateral area of valves rather 

 indistinct. 



2. M. picea, Sow. III. f. 147. West Indies. 



3. M. spinigera, Sow. III. f. 68. Peru. 



4. M. Owenii. Gambia. 



5. M. spinosa, Sow. III. f. 151. Australia. 



6. M. brevispinosa, A. Adams, Gen. Moll. t. 54. f. 1 ; Sow. III. f. 136. 



Island of Johanna. 



7. M. magnifies Sow. III. f. 52. 



11. COREPHIUM. 



Mantle with shelly spines ; valves broad, exposed ; plates of in- 

 sertion of the anterior valve lobed and pectinated, of central valves 

 with a single nick, of hinder valve distinct, slightly denticulated, 

 with one small central slit, not lobed on the sides ; hinder valve 

 oblong, with a subcentral, subposterior, not produced apex. 



i. C. echinatum, Soiv. III. f. 47. 



2. C. ?, Cuvier, t. 154. f. 6. 



3. C? asellus, Forbes fy Hanley, t. A. A. f, 5. 



4. C? rubrum, Forbes fy Hanley, t. A. A. f. 6. 



12. Onythochiton. 



Mantle covered with shelly spines, bristles or chaff-like scales; 

 valves broad, exposed, thick ; plates of insertion of anterior valve 

 lobed, of middle valves one-nicked on each side, of the hinder valve 

 rounded, entire ; posterior valve with a produced terminal apex. 



1. O. Gaimardi. 



2. O. hirtosus. 



3. O. undulatus. Van Diemen's Land. 



13. Molpalia. 



Mantle moderately broad, spinulose ; front edge often expanded 

 and produced, narrow behind (and slightly notched ?) ; exposed part 

 of the valves broad, transverse, depressed ; plates of insertion mode- 

 rate, of the front valve lobed, pectinate, of the hinder valve expanded 

 like those of the lateral valve, and two-lobed ; the hinder valve with 

 a rounded lobe on the hinder edge. 



f Mantle moderately wide in front. 



1. M. Hindsii, A. Adams, Gen. Moll. t. 54. f. 7. 



2. M. Simpsoni. 



ft M<i a lie very wide, expanded in front. 

 I. \1. Bkinvillii. 



