with Descriptions of the new Species. 373 



distinct. Ligament just within the cardinal edge, over the top of the 

 cartilage, and not separated from it by any shelly plate ; and partly hid from 

 view by the upper edge of the hinge margin. 



A. Lateral Teeth short, smooth. 

 a. Shell thickened. Hinder Slojje slightly indicated. 



1. Spisida striatella ; Mactra striatella Lam. 



2. Spisida frdgilis ; Mactra fragilis Chemn , vi. f. 235.; M. brasiliana Lam., 

 No. 27. 



3. Spisida similis ; Mactra sfmilis Gray, Wood Cat. Sup., t. 1. f. 5. Shell 

 oblong-ovate, rather thin, pale reddish white, covered with a thin olive 

 periostraca. The lateral teeth short, triangular, close. 



Inhabits Van Dieman's Land. 



b. Shell thin. Hinder Slope slightly rugidose. The lateral Teeth oblique ; and 



the anterior Hinge Tooth of the left Valve double. 

 * Shell smooth. 



4. Spisida tcnera ; Mactra tenera Humph., Wood Cat. Sup., 1. 1. f. 4. ; M. as- 

 persa Soiu. Tank. Cat., No. 117. Shell compressed, rather solid; white, 

 dark -speckled, front part concentrically grooved. 



Inhabits . 



5. Spisida e/ongdta ; Mactra elongata Quoy Voy. Astrol. Shell oblong- 

 ovate, rather solid, pale brown, covered with a rather thin olive perios- 

 traca. The lateral teeth close, rather short ; the front one notched; hinder 

 rather triangular. 



Inhabits New Zealand. 



6. Spisida pellucida ; Mactra pellucida Chemn., vi. f. 234. ; M. depressa 

 Lamk., No. 29., not Desh. ; M. dealbata Montag., T. B. t. 5. f. 1. 



Inhabits Brazil. 



** Shell radiately ribbed. 



7. Spisida nicobarica; Mactra nicobarica Gmel. ; M. rugosa var. Chemn., 

 vi. f. 237.; Dillwyn, 145. 



8. Spisida Soldnderi; Mactra Soldnderi Gr. ; M. carinata Sola?ider MSS. 

 Hinder slope strongly keeled. 



9. Spisula cegyptiaca; Mactra aegyptiaca Chemn. ; xi. f. 1955, 1956.; Dill- 

 tvyn, 145. No. 35. 



c. The Shell thick, solid. Hinder Slope rugidose, very like former, but the 

 anterior lateral Tooth is nearly perpendicular. The anterior Hinge Tooth 

 of the left Valve compressed, niched. 



10. Spisula rugosa; Lutraria rugosa Lamk., No. 3.; Mactra rugosa Gmel., 

 Chemn., vi. f. 236, 237. ; Encyc. Meth., 254. 



11. Spisula Lamar ckii ; Lutraria rugosa var. b. Lamk. 



Inhabits St. Domingo. 



B. Lateral Teeth cross-ribbed, elongate. 

 a. Front and hinder Slope smooth. 



12. Spisida solidissima ; Mactra solidlssima Chemn., x. f. 1656., Dillw.; 

 M. gigantea Lamk., No. 1.; Encyc. Meth., t. 259. f. 1. 



Inhabits North America. Called the Clam. Is found washed on shore 

 alive on the Long Island, New York. Is considered a delicacy; and the 

 shells are employed by the dairy-women as skimmers. They are said to be 

 found in the stomach of theBalas na. Mitchell 'in Sdliman 's Journal, x. 288. 



13. Spisula Sdyii ; Mactra Sayii Gray. Shell smooth, rather compressed. 



Inhabits Florida. 



e e 3 



