73 



The genus Chonctes is nearly allied to Producta, from which it is distinguished by its arti- 

 culated valves and row of tubular spines t>n the margin of the ventral area, as well as by other 

 characters of less importance. The spines, unfortunately, are preserved only in the smaller 

 number of specimens, and thus the affinities of a given example have often to be decid. <! apart 

 from this character. Even in the absence of this, however, (.'hn>t>.- mav generally be distin- 

 guished with ease from I'mi/ni-tn by the fact that the ventral valve is proportionately lc.-.-> 

 jilibous and ventricose, and the surface striation is finer. On the other hand, the genus 

 (hi, inli.< in form and external appearance makes an approach to the genera Rtri>/iftf'>n>i'H and 

 Leptcena, and it may thus be regarded as being to some extent a link between the families of 

 the $tri'1i"ii ni'l" and I'r<x/iirt/- 



Six or seven species of Chonetes occur in the Corniferous and Hamilton formations of 

 Canada, of which one, viz., C. kemispherica has previously been recorded by Mr. Hillings 

 and all are found in the same formations in the State of New York. 



85. CHONETES LINEATA (Vanuxem). 



$fr"ji?t<unot" lim'/ifti fYanuxem), Ceol. Report of the 3rd District, New York, p. 139, Fig. 6. 

 Chonetes pfczftro (Hall), Tenth Keport on the State Cabinet, p. 117. 

 ! neata (Hall), Pal. N. Y. Vol. IV. p. li>l, PI. XX. Fig. 3. 



Shell semi-oval, the length about four-fifths of the width ; hinge line equal to the '.-neatest 

 width of the shell, and forming about right angles with the sides of the shell. Ventral valve 

 very convex, or ventricose, regularly curved from the umbo to the front, the cardinal angles 

 sli<_ r htlv flattened. The sides of the ventral valve nearly straight and the front margin broadly 

 rounded. The dorsal valve concave, the concavity being le-> tlnn the convexity of the ven- 

 tral valve. Area of both valves very narrow, that of the dorsal valve linear. Cardinal spines 

 rarely preserved, small, slightly oblique to the hinge line, rarely more than two or three visible 

 on eaeh side of the hinge line. Surface marked \vitlj numerous slightly elevated rounded 

 striae, about ten in the space of one line, which increase in Dumber bv bifurcation and inter- 

 culation in proceeding from the beak to the margin. In well pi. -er\vd specimens extremely 

 fine concentric stri;e can also be observed. The interior of the dorsal valve exhibits lines of 

 pustules, corresponding with the striae outside. 



' i- of not uncommon occurrence 



in the 1'evonian Kocks of < 'anada, both in the ( 'or- 



oiferous Limestone and the Hamilton formation, 

 but especially in the latter. Average examples have 

 a width of live lines and a leniithof about four line-. 

 It is readily distinguished by its general form and 



. ,- , . -urface characters, and it M-.MIIS verv probable that 



a. \entral rmlve '! (h-mit.-* lineal*, Hall, natural 1/1 i* 



L! v:ilv,-,,f U,,. -.,,.-. ;ifl.T Hall, i-nl:irL-.-<l the Cl ' '^ Hal] (lal. N. \.. \ol. 



SStSXSf* I*, ]>1 ** ' - "Othing more than a var^ty 



ol' till- .-peeic-. 



/ -///'/// inn! fn/i>if!,i. Corniferoii< l-inn'stone of 1 la'_ r ei>ville and I'ort ( 'oll>.>ni'. 

 Abundant in th- Hamilton Formation of Hartlett's Mill, near Arkona. in the '!'.. n-hip of 

 BosainjUet. 



87. < 'iHiNKTKS M'lTri.A ( llalli. 



(/ : 'ilnl,i (\\:\\\,, Ti'nlh //, nnrl ,.n th, S/<>! '. p. M7. 



Ball Pal N V.. Vol. iv , I'l. XXI., Kg \. 



Slid! small. M-nii c,\ :il ,,r -rmi circular, the width e\o c.lin the len-th by from one fourth 

 to nearly a third (n-ually about live line- in width, bv tlipe and a half in length). I lit 

 line usually not quite eijiial to the L-I'C ale-t width of the -liell, L'eneially producing raotangnlai 

 Cardinal angles. Sido nearly straight; anterior maririn roimdeil broadly \'iitral valve 



<-on\ex. depre--i-rl tc,\\:,rils tl irdinal airjle- i >ometim-- P ni .rl\ curved l'rointl,e ).. ik to 



tin- fiont. -onietirnes \\it|, ; , -li._-l,t nie-ial ilepr.---.ii.ii ahno-t appr..a. bin a r.-.Milar ,-inu - I or- 



:il Valve Very conc-a\e, cln-elv applied tu (lie cnli ..(' the Vclitl.il Vil\.. \ rea ot' the 



cniral valve, narrow, br..ade-t in tin- middle it- plane cnineidiie_' svith tliat of the cardinal an- 



_'!.-- I'oranieii p .rtially oloft d bv a OOnV( \ d. -It id iu m. parti ill v till, d with th-- cardinal 



uf the dorsal valve ; it- -liape br. .adl v t riaii'/ular. I > >i - al ar. i lin. .n . al...ut half the w idth 



