OF CONCHOLOGY. 23 



DESCRIPTIONS OF NEW SPECIES OF MARINE BIVALVE 

 MOLLUSCA IN THE COLLECTION OF THE ACADEMY 

 OF NATURAL SCIENCES.— No. 2. 



BY GEO. W. TRYON, JR. 



7. Macha Wilsonii, Tryon.— Plate 1, fig. 2. 



Deseriptmi. — Shell oval-oblong convex, anteriorly broadly 

 obliquely rounded, posteriorly truncately rounded, white under 

 a light corneous epidermis, with rugose growth-striae, and with 

 raised oblique irregularly curved lines extending from the poste- 

 rior dorsal margin towards the central part of the ventral margin, 

 most of them abruptly angled before reaching the margin, and 

 thence ascending again obliquely towards the anterior dorsal 

 margin. Umbones not very prominent, situated at a little more 

 than one-third the total length from the anterior end. Dorsal 

 margin a little incurved and descending posteriorly. Ventral 

 margin also slightly incurved in the middle. Within glossy 

 white. 



Dimensions. — Width 3-25. Length 1-50 inches. 



ffab. — China. 



Observations. — This is a common species, frequently met with 

 in boxes of Chinese shells, yet strangely overlooked by the con- 

 chologists. In form and sculpture it resembles the Mediterra- 

 nean 31. strigiUatus, but it is larger, more solid and white. 

 Named in compliment to the late Dr. Thomas B. Wilson, a gen- 

 tleman who took great interest in conchology, and to whose 

 liberality the Museum of the Academy of Natural Sciences is 

 largely indebted. 



8. DoNAX [Serrula) pictus, Tryon. — Plate 1, fig. 1. 

 Description. — Shell convex, obtusely wedge-shaped, broadly 



truncate behind, anteriorly rounded ; posterior angle prominent 

 but rounded ; ventrally somewhat arcuated ; umbones prominent ; 



