BRAOHIOPODA. 401 



Rafinesqulna mitmesotensis.l 



RAFINESQUINA MINNESOTENSIS N, H. Winchell. 



PLATE XXXI. FIGS. 25-29. 



1844. Strophomena deltoidea OWEN (not CONBAD). Geological Exploration of Iowa, Wisconsin 



and Illinois, pi. xvi, fig. 8; pi. xvn, flg. 6. 



1852. Leptcena deltoidea OWEN (not CONEAD). Geological Report of Wisconsin, Iowa and Min- 

 nesota, p. 620, tab. 2B, flg. 10 (not the middle figure). 



1862, Strophomena incrassata HALL (not 1847). Geology of Wisconsin, vol. i, p. 42, flg. 16. 



1873. Leptcena deltoidea N. H. WINCHELL. First Annual Report of the Geological and Natural 



History Survey of Minnesota, p. 101; Ibidem, Fifth Report, p. 148; 

 Ibidem, Eighth Report, p. 62. 



1881. Strophomena minnesotensis N. H. WINCHELL. Ibidem, Ninth Report, p. 120. 



1883. Strophomena incrassata HALL (not 1847). Second Annual Report New York State Geologist, 



pi. xxxvin, flgs. 1-5. 



1892. Rafinesquina incrassata HALL. Paleontology of New York, vol. viii, p. 281, pi. vin, flgs 1-5. 



Compare Leptcena incrassata HALL. Paleontology of New York, vol. i, p. 19, pi. iv bis, flgs. 2a-2d, 



1847. 



Original description: "Shell semioblong or semioval, with the cardinal angle 

 about 90, or less than 90; diameter from six to nine lines transversely, and from 

 four and a half to eight lines perpendicularly [Wisconsin specimens attain a greater 

 size] ; the receiving [ventral] valve convex, sometimes more suddenly deflected after 

 passing the visceral area; entering [dorsal] valve gently concave, but reflexed more 

 rapidly about the margin; the exterior of the convex [ventral] valve marked by fine, 

 radiating striae, every third, fourth or fifth one being larger than the intervening ones; 

 interior of the convex [ventral] valve, which is best known from its frequent casts, 

 shows a large muscular impression much resembling that of S. alternata as figured 

 by Meek in vol. i, Pal. Ohio, plate vu, fig. 3c, but somewhat bilobate in front and 

 larger in proportion to the size of the valve; scars of adductor muscles closely 

 approximate, small and in many casts of this valve undistinguishable; behind they 

 are separated (on the casts) by a short mesial ridge, which between them becomes a 

 narrow mesial furrow and then a deep furrow, terminating at the sinus between the 

 outer larger scars; the outer larger scars [diductors] are radiately striated from the 

 beak [at the base of the dental lamellae small adjusters are occasionally indicated]; 

 their margins are strongly marked (on the cast) along their posterior sides by dis- 

 tinct grooves formed by the dental plates, which diverge at once from the foramen 

 at an angle of 100-120, running nearly straight to the outer margins of the muscular 

 scar, when they curve slightly towards the front; the anterior and lateral margins 

 of the general muscular impression are slightly marked on the casts; outside of the 

 muscular scar is a shallow marginal impressed line which is most evident at the 

 cardinal angles as it converges toward the beak; interior edge of the cardinal line 

 is carinate from the teeth to the cardinal angles; the details of the markings in the 

 apex of the beak are seen on the valve itself to consist of two short, distinct, 

 diverging ridges extending not much beyond the hinge teeth [enclosing the adductor 



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