71 



muscular fibres; the inner socket walls are considerably prolonged into the ca\ity of ti. -hell, 

 under the shape of projecting l.imina-, tft the extremity of which free tl -by spiral arm- I 

 perhaps, have beeu affixed. Under this shelly proces- a longitudinal rid.e -ep arates tin- 

 quadruple impressions of the adductor, which on each sidi- form- two deep oval di-pr ions, 

 placed obliquely one above the other, and separated by lateral riiL r c-> branchm.' from the 

 centre one." (l>avid-on, Brit. I'". Brachiopoda, Introduction, p. ll(i'). 



The irenus o/-////x is very nearly related to Strophomena, from which tin- more typical 

 forms may in L'em-ral be ea-ilv - pirit.-l by their usually trivater convexity. and the rounder 

 and shorter hioge-liae. Two species of the genus, viz.: LiVia and 0. / have been 



recorded by .Mr. Billing- a- occurrim: in the Devonian Rocks of Ontario, and both oftl 

 liave cnnie under mv ol.-ervattou. 



,^ 1. OuTIIIs LIVIA (Killm . 



/ (Billiti'.:- Journal, New Series, Vol. V. p. 267, KL- 14-16. 



Orf/f'* L-'i. (0 (Hall , Pal. New York, Vol. IV.. Fige 1 I . 



Sub-orbicular or sub-quadrate : length aliour eijit ninths of the width : _ width. 



u-uallv a little in front of the middle ; lenirth of hin-e inn-, one hail' t.i two third- tlie width 

 of the -hdl ; cardinal extremiti. - rounded ; side- in mo-t specimens somewhat straight. often 

 sufficiently curved to irive a circular aspect to the shell ; front angles ohtuselv rounded ; front 

 niar<_ r in in -eneral broadly convex, sometimes with a small space in the middle in-ar.y -traLht. 

 |)or-il valve of a medium convexity, most elevated about the middle ; the outline formiiiLT a 

 uniform arch from the depressed beak to the front maririn ; the slope from the umbo toward.- 

 the cardinal angles, gently concave; sometimes a barely perceptible mesial depression, com 

 menciiiL' in a point at the beak, and becoming obsolete at One-half or two-third- the length : 

 are:i -ma!i. lviii'_ r in the plane of the lateral mar-ins ; beak minute, forming a -mall triangular 

 projection, ri-inir scarcely one-fourth of a Hue above the . djeol'the are i the point not ineni 

 over, but situated in the plane of the area. Ventral valve moderately convex, most el 

 ..t betWi in one-fourth and one third the length from the beak, thenoe descending with a -.iini- 

 what nit fir ireutly convex -lope, to the front and -ide-. and with a more Sudden and som A hit 

 cone to the hi nire line and cardinal angles; the umbo small, prominent, neatly 



defined, terminating in a small rounded beak, which i- incurved so as to overhang the 

 the area, either not at all or scarcely one tenth of a line ; area triangular, about one i urth 



T than that of the dor-al valve, formintr an anirle of about lu.'i with the plane ni the 

 lateral margin. The f"nm<-n not ol.-rrved. but appear- to be wider than hi-h. On look 

 at the d"l'-d Valve in ;i direction perpendicular to the plane of the shell, the -in all l 



umbo , ,f the ventral valve can be seen rising about one-third of a line above the .lor- ii \> 



Surface with small -ub an-ular radiating rid-es. of nearly a uniform -i/.e, from .-i-dt 

 to ten in tin- width of three lines, increa-in- by bifurcation, strongly curved outward- to the 

 upper part of the -ide- and cardinal angles, the intervening grooves BUD-anguiar in the b .rtom. 

 QQ equal to the nd-_'e- in width. In very perfect -pe.-imen-. very line coneen'iic -u 



ir con.-eiitrie -tri:i- are vi.-ible, seven or ei-lit to one line. In certain condition- of pi . 

 vation :d-o. the radiatiii-_' rid-j. - are -e,-n to \\<- -uli lutmlar. and exhibit numenm- -m .,; 



or circular openinge on their edges each about tin- eighth or tenth of a line in width, and 



from one fourth to two third- of a line di-tant Inun each other. 



Width of larje-i -pe.-iiu.-M examined, ei-hte, n lin- - ; length thick! 



or depth of both valve-, seven line- , height of area oj \entral valve at the beak, one line 



dor-al valve four-fifths of a line; distance between the beaks, one line ; length of hinge-line, ten 

 line- The most common size ap| to be one inch in width. The beak of the ventral dvt- 



i-i incurved, -o that it \\ould toueh a plane projected i' -iiy throiiL-h tin- \.ii\c. at one 



tin d<-plh of the cavity. 



lii ome IpecimeUB the ventral v.dveha- a faint, barely perceptible me-i.il fold, extend 

 ' from the umbo toward.- the front." ( Killing ). 



I have \ery little to add to tin- abo\e e\h,u-ti'.e ile-.-ri|ition of it I by Ml 



lin^r-. tin- only two additional point- of importance that 1 ha\e ,.|.-,-r\ed b in tin- ' 

 in-: 1. 'I'h'- foramen i- \--ry 1 \rj<-, and i- more than tu wple.it the |, i-,,- a- it i- |, 



II. The mar_'in of the -ln-11 ex .ibit-, in adult -peeiin r d well m irke^l concentric ia.i 



oss th, which are <juite independent oi the line concentric -tri.e which -om, . \ i m pie- pr, . ut. 



