234 CONTRIBUTIONS TO CANADIAN PAL.KONTOLOGY. 



being very closely and regularly disposed, as well as slightly undu- 

 lating when viewed with a lens. 



Characters of the interior unknown, though in some specimens there 

 are indications of a mesial septum in the dorsal valve, which appears 

 to have extended from the beaks about half way to the front margin. 



The dimensions of the three specimens figured are as follows: — The 

 one represented by tig, G, length, twelve millimetres; breadth, fourteen 

 mm. and a half ; thickness, six mm. and a half: by fig. 7, length, 

 eleven mm. and a half; breadth, fifteen mm. ; thickness, four mm., and 

 a half: and by fig. 8, length, fifteen mm. ; breadth, sixteen mm.; and 

 thickness, nine. 



Haj' Eiver, forty miles above its mouth, E. G. McConnell, 1887 : 

 fifteen separate specimens and a small jiiece of rock consisting of an 

 agglomeration of many others. 



As the characters of the interior of the valves are unknown, it is of 

 course doubtful to what genus this species should be referred. It i^ 

 here provisionally regarded as an Eatonia on account of the strong I'e- 

 semblancc that the specimens bear externally to some forms of the 

 E. medialis of the Lower Heldei-bei-g limestone of the State of New 

 York, of which it is just ])0ssible that thej' may prove to be a dwarf 

 variety. 



PENTA.irERus GALEATUS, Dalman. Var. 



Plate 30, fig. 2. 



Alrypij ynleiita, Dalman. 1S27. Ivonigl. Vetens. Acad. Haiidlingar, p. 130. 

 Fentami nis rjiilcatus, L'avidson. 1865. Mon. Brit. Silur. Brach., p. 145 (wljicli 

 see for a full list of synonyms of tfiis species up to date), pi. 

 XV, figs. 1.3-23. 

 FenlameruK ijalealuH, Zittel. 188:!. Handbucli dci' ?ali>'ont., vol. f, p. G03, fig- 

 '534. 



Mackenzie Ei\er, at the " Eamparts'' E. (t. McConnell, ISSS: a 

 single and ajjparently somewhat immature specimen, which, however, 

 is strikingly' similar to the Devonian variety of P (jnleatus, from 

 (rerolstein on the Eifel, figured by Zittel in the volume cited abfivc. It 

 differs from P. comis, Owen (which is possibly only another variety of 

 P. gakat'us), principally in the gieatly produced umbo and strongly 

 I'ecurved beak- of its ventral valve. The shallow mesial sinus in the 

 fiont of its dorsal valve is bent abi'uptly inwai'd at almost :i right angle 

 to the rest of the valve and boars a single faint plication in the middle, 



