418 MISSISSIPPIAN BRACHIOPODA 



in all those characters which can be observed, with such punctate shells 

 as Spiriferella neglecta. It has the same rotund form with short hinge- 

 line and ill-defined cardinal area, and if it should be shown that it pos- 

 sesses greatly elongate dental lamella? in the pedicle valve, without a 

 median septum, the reference to Spiriferella, as used in this place, is doubt- 

 less correct. 



Horizon. Lower Burlington limestone. 



Genus ACANTHOSPIKA n. gen. 



Description. Shell small, spiriferoid in form, and so far as known 

 agreeing entirely with Spirifer in its internal characters and in its 

 larger external features. The essential generic character consists in the 

 presence of fine spines upon the surface, which in the genotype are ar- 

 ranged in regularly radiating series along the summits of the plications, 

 and in similar rows on the fold and sinus. 



Remarks. This genus is established upon a single species which has 

 been referred to Spiriferina by its original author, but the shell structure 

 is apparently non-punctate and there is no evidence of a median septum 

 in the pedicle valve. The presence of surface spines, such as the species 

 possesses, is entirely foreign to the genus Spirifer, and consequently the 

 shell has been made the type of a new genus. 



ACANTHOSPIRA ACICULIFERA (Rowley) 



Plate XXXV, Figs. 64-72 



1893. Spirifera aciculifera Rowley, Am. Geol., vol. 12, p. 307, pi. 14, figs. 



13-14. 

 1908. Spiriferina aciculifera Rowley, Mo. Bureau Geol. and Mines, vol. 8, 



2nd ser., p. 84, pi. 18, figs. 13-15. 



Description. Shell small, broader than long, semicircular in outline, 

 hinge-line a little shorter than the greatest width, the cardinal extremities 

 a little rounded. The dimensions of the holotype are: length of pedicle 

 valve 4.1 mm., length of brachial valve 3.9 mm., greatest width 5.6 mm., 

 thickness 3 mm., length of hinge-line 4.8 mm., height of cardinal area 1.2 

 mm., width of mesial sinus in front 2 mm. 



Pedicle valve subpyramidal in form, most prominent in the umbonal 

 region, the surface sloping from the uinbo to the lateral margins in nearly 

 straight or slightly concave lines, the curvature to the antero-lateral and 

 anterior margins gently convex ; mesial sinus non-plicate, sharply defined, 

 originating at the beak, rather shallow, flattened in the bottom ; beak 

 small, moderately incurved; cardinal area moderately high, nearly flat 

 below, becoming concave towards the beak, the lower flattened portion 

 lying in nearly a right angle to the plane of the valve, the lateral mar- 

 gins not sharply defined, the surface curving into the lateral slopes of 

 the valve; an inner or secondary area is present, bounded laterally by a 



