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TRENTON LIMESTONE. 235 



Genus P L A TYN TUS (Conrad).* 



" Depressed, apparently not contractile ; buckler with oculiferous tubercles situated on 

 the front or middle lobe ; abdomen with about 12 articulations ; mesial and lateral lobes 

 depressed ; ribs with oblique grooves." 



This description may be amended, so as to read : Buckler five-lobed, or with the central 

 lobe trilobate ; oculiform tubercles situated on the outside of the lateral divisions of the 

 middle lobe (or of the inner lateral lobes) ; thorax with 11 articulations. 



( These characters will be more fully illustrated under the descriptions of the genera of 

 Trilobites.) 



Thig genus was founded by Mr. Conrad, for the reception of the Paradoxides holtoni of 

 the Niagara group. It is clearly distinct from any other established genus, unless it may be 

 the Lichas of Dalman. The following species is clearly referable to this genus, possessing 

 a very similar character to the P. boltoni. It is also probably identical with JVuttainia 

 hibemica of Capt. Portlock, cited below, being a species of the same genus. f 



296. 1. PLATYNOTUS TRENTONENSIS. 



Pi.. LXIV. Figs. 1 a, b, c, d, e, 



^taphusl trentoturuis. Conbad, Jour. Acad, Nat. Sciences, 1842, Vol. viii, pag. 277, pi. 10, fig. 10. 

 Compare .M\Utainia hibemica, Portxock, Geol. Rep. Londonderry, 1S13, pag. 274, pi. 4, fig. 1 a, b, c, d ; 



and pi. 5, figs. 1,2, 3. 



Buckler ventricose, granulated or pustulate, somewhat five-lobed ; glabella clavate, 

 narrow behind, arched and expanded in front, extending beyond the centre of the inner 



• Ann. GeoL Rep. New- York, 183S, p. 118. 



t The very curious reasoning adopted by Capt. Porti.ock in establishing the Genus ^Tuttainia of Eaton, has 

 induced me to give the generic description of Platynotus in this place. 



The Genus JVultainia of Eatoi* was founded upon a specimen of Trinucleus obtained from the slates of the 

 Hudson-river group, near Waterford (New-York), the one which Green afterwards acknowledged to have received 

 from Eatow, being the same species on which he founded his Genus Cryptolithus. The JVuttainia sparsa of Eaton 

 was a specimen of the central lobe of the buckler of Dipleura (Homalonotus) dekayi, preserving a very prominent 

 elevated band or articulation at the base, which was mistaken for the front of the buckler. Both the specimens 

 alluded to were collected by myself, and are still in my cabinet. 



Although the descriptions of Eaton may have been imperfect, there was no reason for removing the species JV. 

 coneentriea (o the Genus Cryptolithus ; and still less, if possible, for allowing the other fragment to remain as the 

 representative of the Genus JVitttainia, when it is unequivocally a part of the Dipleura dekayi. Neither do I con- 

 ceive it proper to attempt to restore the Genus JWittairria, by applying the name to so entirely different a form from 

 that intended by its author, even should J\r. hibemica be found generically distinct from Platynotus. That genus 

 must remain as a synonym of Trinucleut, which has priority of date ; though A'uttainia was established before 

 Cryptolithus, and, after Trinucleus, is the most appropriate name. The Genus Metopias of Eichwald may, perhaps, 

 be identical with Platynotus ; but I have not seen his description of figi^res. 



The fact that the Genus Platynotus is already in u^e among the C^leoptera, is not a sufficient argument for 

 rejecting it in this place. 



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