222 DE. T. DAVIDSON ON RECENT BEACHIOPODA. 



fully by Sowerby, Reeve, and Dall. In 1870 it was selected by Ball as the type of 

 bis genus GlottkUa. When describing G. albkla, he states, at p. 158 of his ' Revision 

 of the Terebratulidaj and Lingulidee,' " This species differs from the typical species of 

 LiiiffulidiB, in the diverging lamella? which support the post-parietals, in the form 

 of the anterior adductor scars, and in its colour. A microscopical examination of the 

 shell gave the following results : — There were no punctures visible with a good light and 

 a power of 900 diameters. The substance of the shell was shown by a cross section to 

 be composed of translucent horny laminae, nearly parallel with one another and separated 

 by layers of white amorphous calcareous matter, which looked much like powdered 

 sugar. There were no tubuli visible after the most careful search ; the horny layers 

 presented faint indications of a partially fibrous structure, but nothing of the kind ex- 

 tended to the calcareous layers. A section of the lamina much resembled the end of a 

 T-rail, with one flange taken ofi' and obliquely inclined. The anterior part of the shell 

 contained less calcareous matter than that nearer the beaks, and the margin seemed 

 entirely horny. The number of horny layers amounted to eight or ten, in the thickest 

 part of the shell. They were not uniform in thickness, but were thinner than the amor- 

 phous calcareous layers." 



Only the central muscular scars are well defined in the interior of the valves. 



Mr. Dall observes, in his report on the Brachiopoda of Alaska in 1877, that GlottkUa 

 albkla " has not been found to the northward of Monterey, though it may yet turn up 

 somewhere. It is usually not over three inches in length, peduncle included. Like 

 other species of Lingulida?, when young, it is free, and burrows in the mud. Adult 

 specimens, with favorable opportunity, often fasten themselves to a pebble or fragment 

 of shell by the distal extremity of the peduncle. This has been also observed with 

 GlottkUa miramklata, Stm., in Morida, by Mr. P. B. Meek, though that species had been 

 supposed to be always free. It would seem probable, from information communicated 

 to me by Mr. Meek, that these creatures are of rapid growth, and live at most but one or 

 two seasons." 



127. Glottidia Palmeri, Dall. (Plate XXVIII. figs. 5, G«.) 



Glottidia {? albida, var.) Palmeri, Dall, American Journal of Conchology, vol. vii. p. 77, 1871. 

 GlottkUa Palmeri, Dall, Proc. Acad. Nat. Sci. Philadelphia, 1873, p. 20L; Davidsou, Brit. Foss. 

 Brack, vol. iv. p. 3G2, figs. 1-4, 1881. 



Shell narrow, elongated, beaks sharply acuminated, sides subparallel, or very slightly 

 curved ; front line nearly straight. Valves very moderately convex, with two obscurely 

 rounded ridges, commencing at the extremity of the beaks, and deviating until they reach 

 the anterior rounded corners of the front of the valves, and with another similar ridge along 

 the median line ; lateral portions of the valves sloping from the deviating ridges to the 

 lateral edges of the shell. Colour creamy white, smooth, glossy, with obscure impressed 

 lines and concentric ones of growth. Shell-structure calcareous and horny. In the 

 interior of the dorsal and ventral valves the septa and muscular impressions are similar 



