No. 2814. 



LIST OF RECENT BRACHIOPODA—DALL. 



289 



H. sladeni. It has been referred to Aetheia Allan-Thomson, but the 

 Tertiary type of that group is figured by Thomson with a cardinal 

 platform, while in the present species the crura are not united medially. 



HEMITHYRIS BARTSCHI, new species. 



Shell pellucid gray, thin, rounded-triangular, attenuated behind, 

 widest near the front edge of the valves, anterior margin straight 

 without a trace of flexure; surface shining, with faint incremental 

 and delicate radial lines visible only by magnification; pedicel valve 

 inflated, arcuate, the apex incurved; the beak with, on each side of 

 the foramen, a small spine or projection directed laterally; pseudo- 

 deltidia wide, meeting in front of the foramen but not quite coales- 

 cent; hinge teeth feeble, supported by the usual props with a narrow 

 cavity between them and the valve; muscular impressions obscure, 

 the inner surface under magnification showing a minute pavement 

 reticulation; brachial valve less convex; hinge plate feeble, divided 

 mesially to the apex, which is somewhat callous; sockets faintly 

 transversely striated; a low septum, less than one-third the length 

 of the valve, extending forward from the cavity of the beak; apoph- 

 yses short, slender, twisted, with a squared extremity; height of 

 pedicel valve 18, width 16, convexity 7 mm.; height of brachial valve 

 16, width 16, convexity 5 mm.; length of septum 5 mm. 



Type locality. — Off Makyan Island, Molucca Pass, in 298 fathoms, 

 sand; Bureau of Fisheries station 5621. 



The two little horns at the sides of the beak of this species are 

 quite peculiar, but are gradually worn off with age. It is named in 

 honor of Dr. Paul Bartsch, to whose untiring energy the success 

 of the collecting is due. This species differs from Compsothyris in 

 that the septum is not bifurcate behind and is not united to any 

 process from below the crura. 



Type.— Csit. No. 239269, U.S.N.M. 



HEMITHYRIS SLADENI Dall. 



Hermthyris sladeni Dall, Trans. Linn. Soc. London, ser. 2, Zoology, vol 13, pt. 3, 

 p. 440, pi. 26, figs. 7-12, 1910. 



Type locality. — Indian Ocean south of the Say a de Malha banks, 

 in 153 to 123 fathoms, station C. 1, of the Sealark Expedition, 1905. 



144382— 20— Proc.N.M. vol.57 19 



