128 H. A. Pilsbry — Littoral Mollusks from Patagonia. 



Pectenid^e. 

 Pecten patagonicus King. 



Myid^e. 

 Sphenia Hatcher i n. sp. PI. I, figs. 5, 6. 



Shell cretaceous and dull, stout, rather strong, moderately 

 inflated, with broad, somewhat truncated, closed anterior, 

 and narrow, abruptly truncate and widely gaping posterior 

 end. Beaks small, in close contact and eroded at the tips, 

 nearly median, being one mm. nearer the posterior than the 

 anterior end ; projecting somewhat above. Dorsal margin 

 highest anterior to the beaks, thence sloping downward and 

 posteriorly ; anterior end widely subtruncate, arcuate ; ventral 

 margin slightly arcuate. Sculpture, line, nearly regular con- 

 centric grooves separating wider intervals on the anterior por- 

 tion of shell, disappearing posteriorly, where there are only 

 some rude, irregular wrinkles at unequal intervals. Face of 

 the chondrophore in right valve directed ventrally ; that of the 

 left valve partially erect. Interior white or stained, porcellan- 

 ous, the adductor scars distinct, pallial line and very broad 

 posterior sinus indistinct. Length 17, altitude 9*5, diam. 7'2 mm . 

 A single specimen collected. The genus has not before been 

 reported from this region to my knowledge. 



Mactkidjs. 

 Mactra (Mactra s. str.) Jousseaumi Mabille and Rochebrune. 

 PI. I, figs. 1, 2, 3. 



The specimen figured, one of several collected, agrees with 

 Mabille and Rochebrune's short and unsatisfactory description* 

 as far as that goes, except in size ; their specimen measuring, 

 length 45, alt. 34, diam. 18 mm . The proportions however are 

 similar, the figured specimen measuring 67, 48, 28 mm . The sub- 

 triangular form, perfectly straight slope of the valve margins 

 in front of the beaks, and obtuse siphonal extremity, as well as 

 the details of hinge structure, are sufficiently shown in the 

 figure. In external texture it is like an old Spisula solidissima> 

 but the thin, light yellowish-olive cuticle adheres in small 

 ragged patches. 



Mytilidje. 



Mytilus magellanicus Gmel. 



Mytilns sp. A single small specimen. 



Mytilus edulis L. 



Terebratellid^e. 



Terebratella dorsata Gmel. 



Academy of Natural Sciences, Philadelphia. 



* Miss. Sci. du Cap Horn, Mollusques, p. 106. 



