34 TESTACEOUS MOLLUSCA. 



M. Saulii. Or ay. Annals. Nat. His. 1. Oval, sub-triangular, 

 very depressed and thin, smooth, polished, sub-equilateral, rounded 

 at the sides, pale yellowish with crowded pale chesnut rays ; slopes 

 not striated, nor depressed, each with a transverse bar of chesnut ; 

 inside uniform white, the lateral teeth laminar and moderately dis- 

 tant, the v-shaped tooth large. 1^. . 2. 



M. Nucleus. Conr. Jour. A. N. S. Phil. 6. t. 11. /. 4. 

 Small, triangular, thick, with an obsolete concentric ridge ; umbones 

 flattened and rectilinear, apices sub-central and very acute ; one of 

 the slopes depressed ; lateral teeth strong ; inside pale brown. J. — 

 New Jersey. 1 



1 See also the M. Cuneata of Chemnitz,/. 215. (D. 135.— W. t. 

 6. /. 10.) figured with the hinge of Mactra and an external carti- 

 lage ! We have given a copy. See too the M. Achatina, Chemnitz. 

 {W.t. 6.f. 20.) 



To this genus may be attached the MtjlinijE of Gray, which are 

 thus characterised in the Magazine of Nat. History for 1837. 

 " Ovate, trigonal, sub-angular at each end. Teeth like Mactra. 

 Siphonal inflection ovate, distinct. Ligament internal! in a tri- 

 angular groove in the upper surface of the deep oblique cartilage 

 pit f quite hidden. 



* Anterior slope circumscribed by a raised line. 



M. Typicus. Gray. Ovate, suborbicular, convex, solid : um- 

 bones wide apart : area lozenge-shaped : lateral teeth very short, 

 high, thick, round : cartilage pit projecting into the cavity of the 

 shell. 



M. Bicolor. Gray in Mag. N. H. 1837. Ovate, rather con- 

 vex, solid, white ; umbones and anterior slope, orange, varied : 

 lateral teeth short, compressed, triangular ; cartilage pit projecting 

 into the cavity of the shell : (in the young, the anterior slope sepa- 

 rated by a distinct line : umbones brownish.) 



* * Trigonal, anterior slope flattened. 



M. Lateralis. Gray. — Mact. L. Say. Jour. A. 2V. S. Phil. 

 2. p. 309.— Gould, f. 34, 5.-— Conr. Am. C. t. 14. f. 2. Very 

 convex, nearly smooth ; the lateral margins flattened, cordate with 

 a straight, sometimes concave profile, the one rounded at the tip, 

 the other longer and less obtuse: umbo sub -central, prominent. 

 i-'io- — N. America. 



M. Donaciformis. Gray. Mag. N. If. 1837. — Beechey. Z. 

 t. 44. f 13. Trigonal, anteriorly sub-cuneiform, posteriorly some- 

 what rounded ; ventricose, white under a thin epidermis : anterior 

 slope flattened, keeled on the edge. 2. — S. Seas. 



