276 



PROCEEDINGS OF THE NATIONAL MUSEUM. 



VOL. 57. 



young ; the base is evenly closely concentrically lamellose ; the pedun- 

 cular area is ovate-lanceolate, deeply impressed, with the opening 

 narrow, elongate, close to the posterior margin and usually separated 

 from it by a thin papyraceous narrow band which is in the majority 

 of dry specimens broken away so that the orifice is not entire, but 

 has the aspect of a sulcus. This species lives near low water and is 

 often exposed in large masses at extreme ebb tides. 



DISCINISCA LAEVIS Sowerbr. 



Orhicula laevis Sowerby, Trans. Linn. Soc, vol. 13, p. 468, pi. 26, figs. 1 a-d, 

 1822. — Reeve, Conch. Icon., Orhicula, pi. 1, figs. 4 a-h, 1862. 



Disdnisca laevis Dall, Bull. Mus. Comp. Zool., vol. 3, No. 1, p. 42, 1871; Amer. 

 Journ. Conch., vol. 7, p. 76, 1871. — Davidson, Men. Rec. Brach., pt. 3, 

 p. 195, pi. 26, figs. 1, 9, 10, 11; 1888. 



Type locality. — Concepcion, Chile, in 6 fathoms. Cuming. The 

 habitat of the original specimen was unknown, but the species was 

 later found as above by Cuming. 



Cat. No. 



Locality. 



Collector. 



Number 

 of speci- 

 mens. 



265794 



11103« 



111029 



37248 



15826 



61364 



264856 



122840 



207698 



17824 



Point Abreojos, Lower California. 

 Point Abreojos, Lower California. 

 Ipolito Point, Lower California... 



No locality 



Cape San Lucas, Lower California . 



Gulf of California 



Sta. Maria Bay, Gulf of California. 



Panama 



Ancon Bay, Peru 



Peru 



B.F 



Hemphill . . . 

 Capt. Porter. 



Xantus 



Mex. Comm 



B.F 



B. F.. 



Peruvian Govt. 

 H. Cuming. . . . 



3 



10 



3 



2 V. 



4 v. 



1 



14 



1 



4 



1 V. 



This species has a rather prominent central septum on the inside 

 of the lower valve. The exterior of this valve is well figured by Reeve 

 (fig. 4b), having low arcuate lamellae starting from the peduncular 

 large depressed area and surrounded by a marginal band of concentric 

 lamellae. The foramen is narrow and not so near the margin as that 

 of D. lamellosa. Davidson's figure 9 is a poor copy of Reeve ; the base 

 shown in figure 11 of Davidson's plate 26, is that of D. lamellosa and 

 not D. laevis. The posterior extremes of the horny part of the valve 

 meet but do not coalesce behind the peduncular area. 



DISCINISCA STRIGATA Broderlp. 



Orhicula strigaia Broderip, Trans. Zool. Soc, vol. 1, p. 143, pi. 23, fig. 1, 1833. 

 Orhicula cumingii Reeve, Conch. Icon., Orhicula, fig. 6, 1862; not of Broderip. — 



Davidson, Ann. Mag. Nat. Hist., ser. 2, vol. 9, p. 276, 1852. 

 Disdnisca strigata Dall, Bull. Mus. Comp. Zool., vol. 3, p. 42, 1871. 

 Disdnisca cumingii Davidson, Mon. Rec. Brach., pt. 3, p. 202, 1888, ex parte. 



Type locality. — Cana Island, Guatemala, 18 fathoms. Cuming. 



