1869.] 157 [Peririns. 



MEASUREMENTS. 



Length of shell 48 mill. Breadth 32 mill. Height 19 mill. 

 " foot 10.6 " " 3 " 



" gills 32 " " 12 " 



" ' palpi 11 " " 4.6 



Most of the specimens are more sharply incurved than Mr. Say's 

 figure. In many the male of a species of Pinnotheres was living. 



Modiola modiolus Linn., Syst. Nat., 1158; Turton, Brit. Biv.; 

 Gould, Invert. Mass., p. 123; De Kay, Moll. N. Y., p. 185, pi. xxiv, 

 fig. 257. Modiola americana Leach. Modiola papuana Lam., An. 

 sans Vert., Vol. vn, p. 17; Say, Am. Conch., p. 199, pi. xlv, 1832. 

 Mytilus barbatus Linn, et Al. 



Not common, and rather small, but finely colored and heavily 

 fringed with epidermal filaments. 



ARCADiE. 



Argina Gray, 1840. 



Argina pexata Gray. Area pexata Say, Am. Conch., p. 93, 

 1822; Gould, Invert. Mass., p. 95, fig. 60; De Kay, Moll. N. Y., p. 

 176, pi. xii, fig. 211. 



Very common just below low water mark, and often found alive 

 on the shore at low tide. Animal with mantle freely open, edge 

 ruffled, dark brown, with interrupted dark lines next the shell, and 

 a row of ocelli; gills triangular, large, pointed behind, deep red, 

 emitting a reddish fluid when the shell is opened; foot pointed 

 behind; before with a straight, sharp edge; deeply grooved beneath, 

 yellow, not very extensile; palpi none. 



Scapharca Gray, 1847. 



Scapharca transversa Say, Am. Conch., p. 93, 1822; Gould, 

 Invert. Mass., p. 96; De Kay, Moll. N. Y., p. 177, pi. xii, fig. 212. 



Not uncommon, though more rare, than the preceding. Animal 

 with mantle open, edge plain, with a row of ocelli; gills dark red or 

 nearly black, attached to broad, white, sickle-shaped supports, curv- 

 ing about the posterior muscle, and, as in the preceding species, 

 ejecting a reddish liquid when the shell is opened; foot bright yellow, 

 heeled, rounded behind, obtusely pointed before, quite large, deeply 

 grooved; when extended triangular, and as long as the shell; palpi 



