67 



As regards the internal characters of this species, according to Professor Hall, ' in 

 the interior of the ventral valve, the occlusor muscular impressions occupy a narrow, sub 

 quadrangular elevated space, ju ; t beneath the apex, whilst the divaricator uriscular imprint- 

 occupy a short broad space on each side, and are limited by nearly vertical or slL'htly 

 curving ridges which have in some degree tin- appearance of dental lamelhe : within the limits 

 of these ridges the muscular imprints are not strongly marked. In the dor-al valve the pos- 

 terior occlusor imprints are broad and extending far towards the cardinal lin<', and often limited 

 externally by alow pustulose ridge; the anterior impressions are small ami narrow, separated 

 by a narrow mesial rid .e, and margined by diverging elevated ridires. which, above the impre 

 sion, are united in the mesial rid.'.- from which proceeds the bifurcating cardinal prot 



S. iiif<jiti<trintii is placed by Hall in 'tis ireim- x ' '/, and is stated to po-- 



foramen ; but Mr. Hillings as.-erts that a small linear foramen is present. In most resp< 



><ii'i appears to be identical, as pointed out by Hall, with /,y//^//" (Orthis) mt<r- 

 //.<, (Phillips), from the Middle Devonian of England and Europe ; and no other distinct- 

 ons can be at present laid down between the two form-, exempt that the latter is upon the w ! 

 somewhat smaller, and that it does not seem. to possess the tine concentric striae of the former. 

 When the internal characters of L. /',//</.<///"//'., are known, other differences may JUT! 

 appear. It may also be doubted, aspointed out by Mr. Billings, if incguistrial '-itieally 



distinct from the Devonian forms described by Hall under the names of >'. textillS and >'. 

 cava. Lastly, >'. inequistriata is do-dy allied to the >'. oat of the I,"\V'-r Ildd--i! 



Rocks, and has decided affinities with the still more ancient N. </// /////< of the Lower Silurian. 

 I am unable to see that there are any differences of specific value between this ami v 

 'i Hall, though the oppo.-ite is maintained by Hall. S. ii<jni>/i-i<if'i ma\ in 



ral be readily recognized by the character- of its surface-ornamentation and by its shape. 



Lo<, ilit'/ mi'/ /''nrmiili'i/i. Cornifeious limestone, Port t'olborne; Lot ti. Con. 1. Wain- 

 way, and generally throughout the ( 'ornifernus and Hamilton formation* of Western 

 ( hitario. 



STROPHOMENA PATERSOM (Hail). 



Xti-"]Jt<i/n,-ii<! i ll:ill), Tenth Report on the State Cabinet, p. 111. 



,sv/-,,y//(, ///(,// J',/f -. Hillings), ,/ .' tofe, New Scries, Vol. VI.. j>. ."-to. 



lig. 115. 



Shell semi-oval, ventral valve convex, depressed towards the cardinal angles, which 

 elightly extended or aurionlate. " Surface marked by distant elevated radiatim- -u-i;r. and 



the intermediate -pa.e- hy undulating tine >tri;e, ami orOBRed l>y short aliruptly arehiiii; 

 wrinkles, which an- interrujited by the .-tmn- i-ailiating>tri;i'. I he liner radiating >triu- on (lie 

 ventral valve are from three to ten or twi Ivc ht-t \\een the -iiMii-jer ones ; \vhil>t on the il.r-al 

 valve the ^j/aces are wider, and there are from ten to tweiit\ liner stria- between the .-troi 



ones. The finer striffi are crossed by equally fine eonoentric -M-ia-, L'ivin_' the entire surface 



i, .lelicately Oanoellated appearance.'" i llail.'l'al. -N . V., Vol. 1\'.. p B 



,S'. /'/ py closely allied !' s ', from which it i- perhaps not s] 



tic-illv <li>tinct. The oniefpointB of distinction are to be found in the -m.ill-.T convexi' . 



the ventral valve in ,S'. 1',, in tin- -reater number <if the line intermediate >tri;e, and 



in the presence of well-marked concentric wrinkles, X. Patarsoni i> al.-o allied to the Siln 



rian 8 '' < of I'ortlock. l-ut tin- latter i- a tl tttcr and MII .Her form. 



Locality and Fon Not uncommon in the Corniferous Lime-tone of I!id:ewa\, 



and 11.1, Wai:, iL.-t. 



S I KMl'llMMl.NA AMI'I.A (Hall). 

 \pfa i Hall , 'I'i nth Import on the State Cabinet, p. 111. 



'iiiiftiit ( Killiiiu' , New 8ei Vol \ I i 



Strophodonta ampla dial! , iv-,l. \ N . Vol \\ . p, 93 I'l. X I \' . ' .- 1 i. 



Shell lar-e. fi-Miii t\fo to three in le, ihc |. n.'th from a fourth to a third 



mi "Val IPT -emi circular, th-- Inn : line U wide..'- \sider than tin || width o| the -hell 



below. Ventral falve OOUOave, with Oonveiitj near tin- bok . d-.r-al valve COD 



with a concavity in. the neighbourhood of tne beak, following the cur\.iturc of the \ei. 



