414: MISSISSIPPIAN BRACHIOPODA 



surface of the cardinal area, this plate extends from the beak nearly to 

 the hinge-line, its cardinal margin being concave. 



Remarks. In its non-plicated fold and sinus, in the transverse plate 

 joining the posterior portions of the dental lamellae, and in the minute 

 surface ornamentation this species resembles members of the genus 

 Syringothyris, to which genus it has sometimes been referred. However, 

 the transverse plate in the delthyrium does not bear a syrinx upon its 

 anterior surface with a projecting point at the median line towards the 

 hinge-line, this feature of the shell being in essential accord with 

 Pseudosyrinx. A similar surface ornamentation is not altogether 

 lacking in the genus Spirifer, as several Devonian species possess it, and a 

 similar transverse plate is also developed in some species of Spirifer, al- 

 though in no other is it known to be so conspicuously developed as here. 

 Ihe characters which differentiate this species from Pseudosyrinx are the 

 rotund form, the lower and more arched cardinal area, and especially the 

 extravagant development of the dental lamellae. The punctate structure 

 of the shell is not commonly well preserved, and in none of the speci- 

 mens examined by the writer has it certainly been seen. Schuchert, 1 

 however, says, ' ' shell structure distinctly punctate, ' ' and he doubtless ob- 

 served it in specimens more favorably preserved than any of those ex- 

 amined by the writer. 



Horizon. Burlington limestone. 



SPIRIPERELLA LATIOR n. sp. 

 Plate LXIII, Figs. 9-10 



Description. Shell large, broader than long, the hinge-line shorter than 

 the greatest width, the cardinal extremities rounded. The dimensions 

 of a nearly complete pedicle valve are : length about 45 mm., greatest width 

 about 68 mm., length of hinge-line about 50 mm., height of cardinal area 

 16 mm. 



Pedicle valve strongly convex, the greatest depth posterior to the 

 middle in the umbonal region, the surface curving with a gentle convexity 

 from the umbo to the anterior and antero-lateral margins, the slope from 

 the umbo to the cardinal extremities being a little concave; the beak 

 pointed and moderately incurved ; the cardinal area large, concave, with 

 the curvature increasing a little towards the beak, the lateral margins 

 not sharply defined, the surface rounding into that of the lateral slopes 

 of the valve ; the delthyrium very large, broadly triangular ; the mesial 

 sinus originating at the beak, growing very broad anteriorly, rather 

 shallow and regularly rounded in the bottom, well defined laterally, not 

 marked by radiating plications; the lateral slopes each marked by from 



l 9th Ann. Rep. N. Y. State Geol. for 1899, p. 37. (1890.) 



