25 American East Coast Arcas 25 



Comp. Zool. Harvard, vol. 43, p. 399, 1908, was found off Culebra Island, West Indies, 

 and near the Azores and in the North Pacific. 



Subgenus Noetia Gray 



Noelia Gray, Syn. Com. Brit. Mus., 1S40. (Dall). 



Subgenus Noetia Dall, Wagner Free Inst. Sci., Trans., vol. 3, pt. 4, p. 616, 1898. 



The Noetias form a distinct division of the Arcas. Dall says the known fossils are 

 all American and the recent species American and Indo-Pacific. The shell is equivalve, 

 the posterior part is separated from the rest of the shell by a distinct umbonal ridge and 

 in A. reversa, the type of the group, is so short that the beaks are posterior. The car- 

 dinal area usually appears twisted on account of its concave anterior part with raised 

 margin and flat posterior part. The ligament is crossed by transverse grooves which 

 usually extend the width of the ligament in front of the beaks but are weaker posteriorly. 

 Behind the ligament is a bare strip of the cardinal area which is usually oblique to the 

 hinge-line, but in A. reversa it Hes between the beaks and the hgament is entirely an- 

 terior. At the anterior end of the hinge and part way between the center and posterior 

 end the teeth are v-shaped. Nearly all the interspaces show a fine interstitial rib. 



Area incile Say 



Plate V, Figures 18, 19, 20, 21, 22, 23, 24, 25 



Area incile Sa.y, Acad. Nat. Sci. Phila., Journ., istser., vol. 4, p. 139, pi. 10, fig. 3, 1824; Conrad, 



Fos. Tert. Form., p. 16, pi. 2, fig. i, 1832; Fos. Med. Tert., p. 56, pi. 29, fig. 5, 1S40. 

 Anoinolocardia (Area) incile Conrad, Acad. Nat. Sci. Phila., Proc. for 1S62, p. 580, 1863. 

 Anadara incile Meek, Miocene Check List, Smith Misc. Coll. (183), p. 6, 1S64. 

 Noetia protcxta Conrad, Kerr's Geol. Rep. N. Car., .^pp. A, p. 19, pi. 3, fig. 5, 1875. 

 Area {Noetia) incile Dall, Wagner Free lust. Sci., Trans., vol. 3, pt. 4, p. 632, 1898. 



"Shell transverely rhomboidal, with about twenty-seven ribs; anterior hinge margin 

 compressed and angulated. 



"Disk prominent from the beaks to the anterior part of the base: ribs with trans- 

 verse granules; those anterior to the middle alternating with very slender and but little 

 prominent lines and with a groove on each : anterior margin longer to the base than the 

 posterior end, and contracted in the middle: series of teeth nearly rectilinear, entire; in- 

 terv-al between the teeth and the apices with a few transverse lines or wrinkles; a single 

 oblique groove from the apex to a little before the middle, and six or seven narrow ones 

 from the teeth outwards behind the apices: beaks placed very far backward: inner mar- 

 margin crenated: muscular impressions a little elevated, posterior one short: basal mar- 

 gin not parallel with the hinge margin * * * ." — Say, 1824. 



In Say's description anterior and posterior are reversed. 



Ribs twenty-seven to thirty-two, one specimen has thirty-four; a fine interstitial rib 

 in the interspaces, sometimes wanting near the middle of the shell; ribs close-set on the 

 anterior part of the shell except near the hinge, broader, higher and with wider inter- 

 spaces about the umbonal ridge; posterior ribs with a longitudinal sulcus; beaks very an- 

 terior, elevated; cardinal area long, the portion occupied by the ligament diamond shaped 



