142 MISSISSIPPIAN BRACHIOPODA 



are the bases of finer appressed spines; the spines themselves are com- 

 monly destroyed, but they are doubtless entirely similar to those of 

 P. punctatus. 



Brachial valve concave, the central concavity narrower at the beak 

 and rapidly broadening towards the front, with the surface somewhat 

 flattened and subauriculate towards the cardinal extremities ; mesial fold 

 absent. Surface marked by concentric bands similar to those of the op- 

 posite valve and with similar appressed spine bases. 



Remarks. This little species is clearly of the type of E. alternatus, 

 from which species it differs chiefly in its much smaller size and in the 

 absence of a mesial sinus in the pedicle valve and fold in the brachial 

 valve. One of the largest examples observed has a length of 18 mm. 



Horizon. Salem limestone. 



ECHINOCONCHUS MORBILLIANUS (Winchell) 



Plate XVIII, Figs. 13-15 



1865. Productus m&rbilliamis Wdnchell, Proc. Acad. Nat. Sci. Phil., p. 

 113. 



Description. Shell small, a little wider than long, the hinge-line shorter 

 than the greatest width, the greatest width anterior to the mid-length, 

 the cardinal extremities obtusely subangular. The dimensions of a nearly 

 complete pedicle valve, the holotype, are : length from hinge-line to front 

 margin 12 mm., length from umbonal region to front margin 13.8 mm., 

 greatest width 14.5 mm., length of hinge-line 12 mm., convexity 6 mm. 



Pedicle valve strongly convex, the greatest depth posterior to the 

 middle, the umbonal region prominent and somewhat protuberant poste- 

 riorly beyond the hinge-line, the surface curving abruptly to the cardinal 

 margin on each side of the beak, and much more gently to the lateral and 

 anterior margins, compressed at the cardinal extremities to form small 

 auricular expansions; mesial sinus obsolete; the beak small, pointed and 

 strongly incurved. Surface marked by regular, concentric bands whose 

 width at the median line of the valve is 1 to 1.5 mm., each band is slightly 

 depressed posteriorly below the anterior margin of the band next behind, 

 and each is marked by the radially arranged and nearly uniform elongate 

 bases of fine, appressed spines, higher in front where the spines have be- 

 come free and becoming obsolete posteriorly at or near the posterior 

 margin of the concentric band ; towards the cardinal extremities the reg- 

 ular arrangement of the concentric bands and spine bases becomes some- 

 what disorganized. 



Brachial valve not known. 



Remarks. This little Echinoconchus most closely resembles the small 

 E. biseriatus of the Salem limestone. These two species are similar in 

 size and in both the mesial sinus is wanting. E. morbillianiis is perhaps 



