I04 NEW YORK STATE MUSEUM 



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tral ; cardinal margin nearly straight or slightly declining each way 

 from beak ; anterior margin abruptly rounded, basal margin broadly 

 and evenly rounded, posterior basal angle subacute, posterior margin 

 gently convex, passing obliquely upward and forward to the 

 obtusely and obscurely angular posterior cardinal extremity. Beak 

 apparently small, situated fairly midway between the cardinal 

 extremities, umbo not very prominent ; umbonal ridge sharply angu- 

 lar. Anterior slope rounded, with a flattening of the nasute anterior 

 extremity; ventral slope evenly rounded; posterior slope concave 

 along the umbonal ridge, abruptly turning into the flat nearly vertical 

 posterior cardinal slope. Surface of anterior and ventral slopes 

 almost smooth, only faint, widely separated growth-lines being visi- 

 ble ; the posterior slope bears five sharp radiating ribs and the pos- 

 terior cardinal slope one or two obscure flat ribs. 



Horizon and locality. Very rare (only, one specimen found) in 

 dark gray sandy shale of Snake Hill beds at Snake hill, Saratoga 

 county, N. Y. 



Remarks. This species is similar in form and size to the shell 

 from the Trenton of Carlisle, Pa., which Hall had referred to the 

 Lorraine species Nuculites poststriata Emmons 

 (title 3, page 151). Ulrich (title 38, page 610) has pointed out that 

 the Trenton Nuculites (now L y r o d e s ma ) poststri- 

 ata and the Lorraine form are not identical, and has referred 

 the Trenton species with some doubt to his Lyrodesma 

 cannonense. Our species is clearly more elongate than any 

 of these. Doctor Ulrich writes me regarding this species : " Though 

 of the same section of genus, this is not the same species as either 

 of the two Lorraine species that are current under the name 

 L. poststriatum. My Black River L. acuminatum is 

 also one of this section and even nearer. The broader and more 

 common of the two Lorraine species to which the name poststriatum 

 should be restricted, would seem to be a larger shell than this Snake 

 Hill species. The latter is not only smaller but is relatively lower 

 (from beak to ventral margin), relatively wider posteriorly and less 

 strongly convex in the ventral part of its outline." 



Hall (op. cit. page 302) cites also Lyrodesma pulchella, 

 a species which typically occurs in the Lorraine beds at Pulaski, 

 as occurring in the " black glazed slates near Waterf ord " and fig- 

 ures (plate 82, fig. i2c) a small specimen from that locality. Since 

 we now know that the shales about Waterford are all of Trenton 

 age, being partly Canajoharie and partly Snake Hill shales, it is 



