26 THE NAUTILUS. 
Subfamily Macrrin. 
Genus MACTRA (L.) Lam., 1799. 
(+ Crassatella [cygnea] Lam., 1799); Type M. stultorum L. 
Mactra Richmondi Dall. Greytown, Nicaragua. 
Subgenus Macrreua Gray, 1853. 
(-+ Papyrina Morch, 1853) ; Type: 
Mactra (Mactrella) alata Spengler, 1802. Porto Rico to Brazil. 
—WM. carinata Lam., 1818; + MM. striatula Auct. non L. 
Subgenus Macrroroma Dall. 
(=Standella Cpr. ex parte, non Gray ; Spissu/a Morch non Gray). 
Anterior left lateral tooth bidentate, right ventral tooth triden- 
tate. | Lype': 
Mactra (Mactrotoma) fragilis Gmelin, 1792, Hatteras to Rio Janeiro. 
—WM. dealbata Pult. 18038; + M. brasiliana Lam., 1818; +. ob- 
longa Say, 1822; +M. ovalina (Lam.?) Auct.; +M. oblongata 
Ravenel, 1834; +. bilineata (C. B. Ads.) Reeve, 1854; +. sili- 
cula Reeve non Desh. (?) 1854; +. ambigua Weink. (?); +. 
anserina Guppy, 1875. Not Spisula fragilis Gray, 1858. 
Genus SPISULA Gray, 1838. 
(=Spissula Phil., 1847, not Morch, 1853 ; + Spizula Conr., 1868 ; 
+ Spisulina Fischer, 1887). Type Mactra solida L., Gray, 1847. 
Subgenus HemimmacrrRa Swainson, 1840. 
Spisula (Hemimactra) solidissima Dillwyn., 1817. Labrador to Virginia. 
—M. gigantea Lam., 1818; --M. procera Sol., mss.; +1. Sayi 
Gray, 1838. 
S$. (Hemimactra) solidissima var. similis Say, 1822. Rhode Id. to St. Thomas, 
W. Indies, 
=WM. Raveneli Conr., 1831; not M. similis Gray, 1828. 
Section Mactromeris Conrad, 1868. 
Spisula (Hemimactra) polynyma Stimpson, 1860. Hudson Bay to Cape Ann, Mass 
=M. ovalis Gld., 1840, not J. Sowerby, 1817; --M. ponderosa 
Phil., 1844, not Eichw. nor Conr., 1830; --M. grandis Desh., 1830, 
not Gmel., 1788; +M. similis Gray, 1828, not Say, 1822; +M. 
Grayana Schrenck, 1867. 
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