714 DEEP WATER MOLLUSES AND BRACHIOPODS—DALL. vol.xvil 



other and united to the upper edge of a rather prominent median sep- 

 tum, forming a spondylium, and in having the brachia consisting of a 

 much smaller number of coils. Tyjie Frieleia halli, Dall. 



FRIELEIA IIALLI, uew species. 

 Plate XXIV, figs. 6, 9, 10, 11, 12, 13. 



Shell of moderate size, thin, translucent, yellowish gray, dorso- 

 ventrally somewhat compressed, slightly impressed in the median 

 line below, but the basal margin hardly, if at all, flexuous; surface 

 smooth, polished, except for faint, irregular radial markings and deli- 

 cate incremental lines, occasionally modified by accidents of growth; 

 pedicle valve pointed above, rounded at the lower corners, with a 

 sharp, short beak slightly recurved, below which is a nearly circular 

 peduncular orifice, bounded below by two well-marked subtriangular 

 deltidial plates, which do not quite meet in the median line; cardinal 

 margin below them evenly arched and passing without an angle 

 into the lateral margins of the valve, which for some distance are 

 almost straight; the margins then round evenly into the base, which in 

 many specimens is nearly straight, in others slightly excavated 

 mesially; the whole of the margins are nearly in one vertical plane; 

 teeth much as in Hemithyris psittacea, short, stout, projecting at 

 right angles to the plane of the valve margins, and slightly recurved, 

 below supported by slender buttresses, which rise from the valve and 

 extend upward into the cavity of the beak, leaving narrow recesses 

 between the buttress and the side of the valve; in the interior of the 

 beak there is no mesial septum, and the thinness and translucency of 

 the polished valve are such that hardly any trace of muscular impres- 

 sions is left on the shell; these impressions, if visible, would extend 

 only three-fourteenths of the distance from the cardinal margin toward 

 the base of the valve, while in H. psittacea the proportion is about 

 eight twenty-firsts ; the interior of the valve under moderate magnifica- 

 tion shows with great clearness the reticulated outlines of the prisma 

 of shelly matter forming the internal layer of the shell, but there are 

 no other internal markings; brachial valve hardly less inflated than 

 the other, roundly pointed above, with a well-defined, slender, sharp- 

 edged medial septum extending six-fifteenths of the distance from the 

 cardinal apex toward the base; teeth long, diverging at an angle of 

 about 120°, obliquely transversely striated, the sockets behind them 

 deep, internally transversely grooved; lamella supporting the teeth 

 deep seated, extending obliquely from the sides of the valve; crura 

 starting from the cardinal margin at the inner ends of the teeth, 

 extending in a straight line obliquely downward and forward, united 

 to the teeth for about half the whole length by an excavated lamina; 

 the free ends of the crura slightly wedge shaped, parallel sided, and 

 abruptly truncate at the ends. From the upper part of the inner edges 

 of the crura on each side an excavated lamina is given off, which 



