48 PALAEONTOLOGY OF NEW YORK. 



of tlic ravs (ill tin- si)friiiR'ii lij^ured) have been affected, apparently, by some 

 iiijiiiv rcceivcMl (hiring the life of the animal, which has also pioihiced a 

 strong varix of growth. 



Li«'amental area l.'> iiiin. widi- at tlie ))eak, whence it diminishes towards 

 the extremities of tlie hinge-line, marked by several Hat, longitudinal striai. 

 Cartilage-pit broa<l-triangular, situated under the apex. 



The .><pecimen described is 7") mm. in lieiglit, SS mm. in longitudinal 

 diameter, and hinge-line -Iti mm. The distance between tlie centres of two 

 of tlie larL^' ravs at tlie Ijasal margin is about 17 mm. 



The surface markings resemble L. tricostatus, but they are stronger, more 

 rugose, and the rays less numerous; also the shell is not oblique, and the tjeak 

 is moi'e obtn.se and roumleil. It differs from L. macrodontus and L. magnificus 

 in its greater convexity, deepiM' byssal sinus, larger posterior ear, and by its 

 surface characters. This remarkably large and fine species shows conspicu- 

 ously the diminished anterior ear, a feature also seen in L. tricosiaim, which is 

 the reverse of many species of recent Pectenidse, where the anterior ears are 

 developed beyond the posterior; as in Janira longicauda (d'Orbignv), and Peden 

 Tranquebaricm (Gmrijn). 



This species, although seen in only oiu' valve, is characterized by its peculiar 

 surface markings and outline. 



Formation and locality. Hamilton grouj), from a liowldei' found near Elmiia. 

 N. Y. 



LVRIOPECTEN TRICOSTATUS. 



PLATE IV. KIG. n ; l'I..VrE VM, KK; Ji; ; ami I'l. AlK \, KI(;s. (Hi. 



Avii-iila Ir'niiMila, V.\.\r.\K.M. (iodhijf. Siirv. N. V. : Rcpoit of Thii-il Uist., p. 179, fi),'. 1. 1843. 

 Lyriiijmteu trUnnUttuJi (Vanuxb.m), Hall. Pal. N. Y., vol. v, jif. 1. Plates ami Explanations: PI. 4, fifr. H ; 



jil. 7. tifT. 2(i ; ])1. 10, Hp). 0-12. Jan., 18S3. 



Shem, large, transverselv and more or less ol)liquely broad-ovate; height 

 usually less than the length, tlie ]iro})ortions varying with the age of the 

 .'<hell ; y(mng specimens are longitudinally elliptical ; iiuiture specimens are 

 more obli(jue ; while some abnormal foi'ins show a difl'erence in the direction 



