618 CAMBEIAN BEACHIOPODA. 



Trematoholus insignis Matthew, Hall and Clarke, 1892, « Eleventh Ann. Kept. State Geologist New York for 1891, 



p. 252, fig. 263. (No text reference. Figs. 263 (la-d) are copied from Matthew, 1893a, figs, la-d, respectively, 



p. 276.) 

 Trematoholus iiisignis Matthew, Hall and Clarke, 1892, « Forty-fifth Ann. Kept. New York St^te Museum for 1891, 



p. 568, fig. 263. (Copy of preceding reference.) 

 Trematoholus insignis Matthew, 1894, Trans. Roy. Soc. Canada for 1893, 1st ser., vol. 11, sec. 4, No. 8, pp. 88-90, 



PL XVI, figs. 4a-d. (Except for the last paragraph, this is a copy of Matthew, 1893a, pp. 276-279. Figs. 4a-d 



are copied from Matthew, 1893a, figs, la-d, respectively, p. 276.) 

 Trematoholus insignis Matthew, 1895, Trans. New York Acad. Sci. for 1894-95, vol. 14, pp. 122-125, PI. IV, figs. 2a-d. 



(Text and figures copied from preceding reference.) 

 Trematoholus insignis Matthew, 1895, Bull. Nat. Hist. Soc. New Brunswick, vol. 3, No. 13, p. 95, figs. la-d. (No 



text reference. Figs, la-d are copied from Matthew, 1895a, PI. IV, figs. 2a-d, respectively.) 

 Trematoholus insignia Matthew, 1898, Bull. Nat. Hist. Soc. New Brunswick, vol. 4, pt. 1, No. 16, p. 35, figs. la-d. 



(No text reference. Figs, la-d are copied from Matthew, 1895a, PI. IV, figs. 2a-d, respectively.) 



Shell subcircular in outline, biconvex, valves inarticulate. Ventral valve gently convex, 

 with the minute beak at the posterior margin, and above a low area. Pedicle opening a rather 

 large, simple, oval opening at the anterior end of a furrow that gradually narrows toward the 

 beak, where it terminates; from the lines of growth in the furrow indicating progressive stages 

 of the advance of the foramen it is evident that Ihe foramen began at or just in advance of the 

 beak, and advanced with the growth of the shell in the same manner as the foramen of Schizam- 

 lon (PI. LXXXIV, fig. 1) ; the length of the foraminal furrow varies from one-third to two- 

 fifths of the length of the valve. 



The substance of the original shell appears to have been entirely removed by solution and 

 replaced by the limestone. The closely related species T. Tcempanum (Matthew) has a calcareo- 

 corneous shell. That the shell was strong is indicated by the depth of the vascular markings 

 and muscle scars. The outer surface is marked by a few concentric lines of growth. The type 

 specimen is 9 mm. in diameter. 



The area of the valve is short and divided midway by a depressed, narrow, subtriangular 

 space, bounded by narrow, slightly elevated ridges that originate just beneath the beak and 

 diverge a little toward the margin of the area, where they unite with the margin and extend 

 forward so as to form two short projections, one on each side of the pseudopedicle furrow on the 

 area; the area slopes forward from the beak at an angle of about 15°; it is marked by rather 

 strong transverse lines of growth. 



There are no traces of the posterior portion of the foraminal furrow on the interior of the 

 valve; it is entirely within the substance of the shell. The splanclinocoele extends to about 

 the center of the valve; in front of the area a low, broad swelling begins that extends forward 

 beyond the foraminal openmg, where it divides so as to leave a short depressed space, and 

 within, a narrow median ridge; on each side and in front of the line of the pedicle opening there 

 are the obscure outlines of the spaces occupied by the scars of the points of attachment of the 

 central, middle lateral, and outside lateral muscles, very much as in Oholus (PI. VII) ; these 

 muscle-bearing spaces are finely shown in T. Icempanum (Matthew) and T. pristinus (Matthew) 

 (PI. LXXXIII, figs. Id, Ij, 2c). The sinuses of the main vascular canals are broad and strong; 

 they start near the front margin of the area near the median line and extend outward and forward 

 subparallel to the outer margin of the valve to about the transverse median line, beyond wliich, 

 owing to the broken specimen, they have not been traced. The umbonal muscle scars occur 

 on each side of the median line just beneath the projections of the area beside the false pedicle 

 furrow; they are small and located on a low ridge. The transmedian and anterior lateral mus- 

 cle scars are elongate oval in outhne, close to the outer margin of the main vascular sinus, and 

 placed on a rounded, low ridge; the transmedian scar extends a little outside of the anterior 

 lateral scar at its anterior end; as already stated, the central scars and the middle and out- 

 side lateral scars probably occurred in the spaces on each side of the anterior end of the low 

 median ridge. 



oThis date (1892) is taken from the title-page and is used througtiout this monograph, but the work is clearly antedated, the correct 

 date being 1893 or 1894. 



