IO6 NEW YORK STATE MUSEUM 



Myalina pterinaeoides Clarke 



Plate 25, figures n-i8; plate 26, figures 1-3 



My al i n a p t er in a eoides Clarke. N. Y. State Mas. Bui. 107. 1907. 1x213 



One of the commoner species at Presque Isle stream is a Myalina with 

 a striking resemblance throughout, save in the character of the hinge, to 

 certain Pterineas with curtailed posterior wing, and specially similar to 

 P t. f o 1 1 m a n n i Freeh. 1 



The frequent internal casts show the species to be devoid of the hinge 

 teeth of Pterinea and present only the moderately broad ligamental stria- 

 tions of Myalina and the abbreviated earless and abrupt front margin. 

 This latter feature is rather feebly developed but when the shell is retained 

 the anterior incurvature with margins truncated and meeting at right angles 

 is evident. In other respects we may note the following characters: The 

 shell is relatively suberect without posterior hinge, obliquely elongate, sub- 

 oval with greatest width across the pallial region, the hinge line being short, 

 not more than one half as long as the length of the shell. The valves are 

 shallow and thick ; posterior muscle scar well denned, situated at one half 

 the length of the shell ; pallial line short, barely reaching beyond the 

 middle ; anterior scar absent. 



The surface of the shell is coarsely rugose in concentric growth lines 

 and is without other ornament. Of such a species as this we know nothing 

 among the faunas of the Appalachian early Devonic. 



Locality. Presque Isle stream. 



Modiomorpha vulcanalis Clarke 



Plate 26, figures 9-11 



Modiomorpha vulcanalis Clarke. N. Y. State Mus. Bui. 107. 1907. 1x219 



Shell robust, with very thick valves; outline short, obliquely cordate, 

 hinge line oblique, beak in front of the middle, not elevated ; umbonal ridge 

 low but distinct, from which the slope anteriorly is broad and very gently 

 convex while posteriorly it is at first gently concave, then depressed and 

 almost flat near the hinge line. The marginal outline is narrow in front at 

 the extremity of the oblique hinge, widens in a low curve backward, turns 

 almost at right angles at the end of the crescence line, curving thence broadly 

 upward and forward, joining the obliquely elevated hinge in a broad curve. 

 The length and width of the shell are nearly the same. 



The resemblance of this species to Drevermann's Goniophora 



'Freeh, op. cit. pi. 10, fig. 5; Drevermann. Fauna d. Untercoblenzsrh, [1.82, pi. 10, 

 fig. i, 2. 



