244 BULLETIN OF THE 
of having a different kind of epidermis; shell extremely inequivalve, not one 
sixth of its surface being anterior to the beaks; hinge line straight; area very 
narrow, its section forming a V-shaped figure, the black part of the ligament 
entirely posterior, generally beginning to show about as far behind the beaks as 
the beaks are behind the anterior end of the hinge line; hinge peculiar, teeth 
transversely grooved, anterior end of the hinge with a few (4-6) teeth, irregu- 
lar or tending to trend with the longest axis of the valve; posterior end with 
four or five elongated teeth nearly parallel with the hinge line; between these 
the hinge is edentulous or faintly irregularly granulous; lon. of figured type 
26.0; max. alt. of do. 14.0; diam. 9.5mm. A specimen obtained by the Fish 
Commission measures 46.0 mm. in length exclusive of the epidermis. 
Dredged living at Station 193, near Martinique, in 169 fms., sand, bottom 
‘temperature 51°; and at Station 300, off Barbados, in 82 fms., bottom temper- 
ature 60° F. 
Foot small, split in the median line; byssal groove large and deep; palpi 
none; a single gill on each side with the broad margin of insertion curled 
downward into a spiral at its posterior end; mantle margin thick, smooth, 
plain, dotted with black posteriorly, otherwise (in spirit) whitish. The dots 
are single, at regular intervals, and look much like ocelli. 
This fine species does not closely resemble any I find described ; it is most 
like a form I find in the collection named Arca (Barbatia) Listert Phil., but 
which is dark colored, very much smaller, less compressed, and otherwise differ- 
ent in various details. The present species belongs to the subgenus Barbatva, 
and for those who give this group a generic value its name would be Barbatia 
ectocomata. 
Arca barbata Linz. 
Arca barbata Linné, Gmelin, Syst. Nat., p. 3306, 1788. 
Young specimens of this well known form were dredged near Barbados, at 
Stations 290 and 292, in 56-73 fms.; and by Sigsbee off Havana in 127 fms. 
(dead valves). It is a shallow-water species and probably does not live in 
more than 100 fms. 
Genus MACRODON Lycert. 
Macrodon asperula Datt. 
Macrodon asperula Dall, Bull. M. C. Z., IX. pp. 20, 1881. 
Plate VIII. Figs. 4, 4 a 
Habitat. Station 33, 1568 fms., in the Gulf of Mexico, bottom temperature 
40°.5 F.; Station 19, 310 fms., off Cuba; Cape San Antonio, 1002 fms., this 
specimen too young to be certain of the identification. 
