'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 shorty smooth. 

 a. Shell thickened. Hinder Slope slightly indicated. 



1. Spisula striatella; Mactra striatella Lam. 



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

 No. 27. 



3. Spisula 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 rugulose. The lateral Teeth oblique; and 



the anterior Hinge Tooth of the left Valve double. 

 * Shell smooth. 



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

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

 dark-speckled, front part concentrically grooved. 



Inhabits . 



5. Spisula elongdta ; 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. Spisula pellucida ; Mactra pellucida Chemn., vi. f. 234.; M. depressa 

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



Inhabits Brazil. 



** Shell radiately ribbed. 



7. Spisula nicobarica ; Mactra nicobarica Gmel. ; M. rugdsa var. Chemn., 

 vi. f. 237.; Dillwyn, 145. 



8. Spisula Soldnderi; Mactra Solanderi Gr. ; M. carinata Solander MSS. 

 Hinder slope strongly keeled. 



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

 wyn, 145. No. 35. 



c. The Shell thick, solid. Hinder Slope rugulose, 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. 



1 1 . Spisula Lamarclcii ; Lutraria rugosa var. b. Lamk. 



Inhabits St. Domingo. 



B. Lateral Teeth cross-ribbed, elongate. 

 a. Front and hinder Slope smooth. 



12. Spisula solidissima ; Mactra solidfssima 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 theBalae'na. Mitchell in Sillimatf s Journal, x. 288. 



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



Inhabits Florida. 



EE 3 



