OF MOLLTJSCA. 183 



opake at the bend, with a spine in front ; lateral teeth 5 on each 

 side, of irregular shape, trapezoid, arranged obliquely, the sixth erect 

 between the second and third, hooked, slightly bent, upper margin 

 reflexed and cut (fig. 98). 



Mr. Clark, who has very imperfectly observed the development of 

 this species, erroneously says it shows no metamorphosis. 



** Mantle covered with imbricate scales, slit behind. 



7. Lorica. 



Mantle very densely covered with small smooth ovate imbricate 

 scales, the hinder edge slit ; valves broad, transverse ; plates of in- 

 sertion of the front few-lobed, of the hinder deeply emarginate and 

 obsoletely lobed ; the hinder valve with a produced acute posterior 

 marginal apex, and notched on its hinder edge. Gills ? 



1. L. Cimolia, Adams, Gen. Moll. t. 54. f. 5, shell only. 



8. Schizochiton. 



Mantle broad, deeply notched behind, covered with small chaff- 

 like scales ; valves elongate, subcordate, narrow ; lateral area short, 

 distinctly defined ; the hinder valve large, with a subposterior superior 

 apex, and a deep notch on its hinder lower edge, and the plate of 

 insertion small, with a few oblique notches, scarcely pectinated. 

 -Gills occupying the hinder half of the side of the foot. 



1. S. incisus, Adams, Gen. Moll. t. 55. f. 6. Philippines. 



*** Margin covered with uniform calcareous thick bristles like 

 spines, entire behind. 



9. ACANTHOPLEURA. 



Margin covered with elongate shelly bristles ; valves thin, broad, 

 close, keeled ; lateral area distinct ; plates of insertion pectinated, of 

 the central valves with a single lobe on each side, of the hinder valve 

 regular, well developed ; last valve entire. 



1. A. Peruviana, Sow. III. f. 44. Peru. 



2. A. bicolor. West Indies. 



3. A. Hennahi, Sow. III. f. 33. 



4. A. Watsonii, Sow. III. f. 81, 82, 130. 



5. A. Hanleyi. 



10. Maugeria. 



Margin covered with elongate shelly spines or bristles ; valves 

 broad, thick, close ; lateral area rather indistinct ; plates of inser- 

 tion pectinated, of central valves with a single notch on each valve, 

 of hinder valve narrow, rather irregular. Gills as long as the sides 

 of the foot. 



