NATURAL SCIENCES OF PHILADELPHIA. 
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to greatest width of shell; mesial sinus wanting or barely perceptible ; exter¬ 
nal surface marked by fine, rigid, sharp, once dichotomizing radial lines or 
ribs, numbering about 40. No indications of spines have been detected. 
Length of hinge line, ’29 (100) ; length from beak to anterior margin, 
•21 (72). 
Described from an imperfect ventral valve ; but its peculiar characters 
easily distinguish it. 
Museum of University of Michigan, Collected by A. Winchell at Valley 
Forge, one and a half miles below Cuyahoga Falls, Ohio. 
Producta duplicostata, n. sp. Shell rather large with subcircular outline. 
Ventral valve very ventricose and greatly arched, with steep slopes to the 
right and left margins, not enlarged at the aperture, and entirely destitute of 
mesial sinus ; marked with numerous interruptedly and irregularly striate 
sinuous ribs, which dichotomize once or twice in the middle region of the 
valve, and towards the front resolve themselves each into a fascicule of three 
or four smaller ribs, themselves raised into a wider rib-like elevation around 
the anterior margin. The tubular spines are scattered over the whole exte¬ 
rior, but become much more abundant at the commencement of the marginal 
costate ridges. The whole exterior of the cast is marked also by oblique 
punctations, which are placed mostly in irregular lines between the ribs, and 
become consequently most abundant toward the margin. On the sides of the 
cast the punctations become elongated into short furrows which cross the 
surface obliquely. 
Length, 1-19; breadth, 1-24; convexity of ventral valve, ‘58; number of 
marginal ridges, 15 to 20. 
Collected by A. Winchell, at Battle Creek, Michigan. Occurs also in Lick¬ 
ing County, Ohio. 
Producta morbilliana, n. sp. Shell smal 1 , transversely subelliptic, only 
moderately produced. Hinge line seven-eighths the greatest width of the 
shell; ears small, nearly right angled. The shell regularly contracts from 
the aperture to- the beak, which is small, subacute, and projects slightly be¬ 
yond the hinge. The arching of the shell is such that when resting on the 
aperture the greatest height is equal to one-half the greatest width. No 
sinus or flattening present. The surface is marked by a series of deep, con¬ 
tinuous, equidistant wrinkles, ten or eleven in number, becoming obscure 
toward the beak ; between the wrinkles are numerous fine concentric striae 
not easily seen without a magnifier. These features are crossed by a longitu¬ 
dinal system which, near the beak, is a set of fine regular costae, which near 
the middle become interrupted by the wrinkles, and, losing their identity, 
result in several concentric bands of short longitudinal tubes buried in the 
substance of the shell, and gradually emerging and presenting their apertures 
anteriorly. 
Transverse diameter of aperture, *58 (100) ; length of hinge line, *51 (88); 
distance from hinge line across the aperture to opposite side, *44 (76); height • 
of shell when resting on the aperture, *26 (45). 
From the base of the Burlington limestone, Burlington, Iowa. “White 
Collection ” of the University of Michigan. 
A cast from the yellow sandstone below (probably “No. 5,”) is probably 
identical with this. 
This beautiful species is most nearly related to P. speciosa, Hall, (xth Rep. 
N. Y. Reg. p, 176.) The resemblance, however, is not striking, except in 
the cast referred to. This differs in having the pustules more regularly ar¬ 
ranged in concentric bands. P. morbilliana may also be compared with P. 
Rogersi, Nor. and Prat., (Jour. Acad. Nat. Sci. Phil. [2] iii. 9, pi. i. 3, a, b, 
c, not P. aspera McChesney.) It is, however, a much neater species, without 
trace of sinus, not so full near the beak, while the rib-like tubes arranged 
1865.] 
