282 CONTRIBUTIONS TO CANADIAN PAL/EONTOLOGY. 



to a hundred can be counted under a lens. In addition to these, the ex- 

 terior of well preserved specimens is marked with exceedingly fine and 

 close-set, concentric raised lines. Interior of the valves minutely papillose. 

 Muscular impressions unknown. 



The dimensions of two average specimens are as follows : of one, maxi- 

 mum length nearly ten millimetres, greatest breadth, nineteen ; of another, 

 length ten mm. and a quarter, breadth twenty. 



Rather abundant at the north end of Manitoba Island, in Lake Mani- 

 toba, where it was collected by Prof. H. Y. Hind in 1858 and by J. B. 

 Tyrrell and the present writer in 1888. 



This small Ghonetes seems to differ from the C. carinata ('or coronata) of 

 Conrad, as described and figured by Prof. Hall in the fourth volume of the 

 Palaeontology of the State of New York, in its uniformly smaller size, 

 flatter and more transversely elongated valves, finer sculpture and in the 

 greater length and smaller number of the spines on the cardinal margin 

 of the ventral valve. According to Prof. Hall, a careful measureof the 

 radiating striae on numerous specimens of C carinata fi'om the State of 

 New York " shows that they range from nine to fifteen striiB in the space 

 of two tenths of an inch,'' while specimens from Illinois gave from nine to 

 twelve in the same space. In three average examples of C. Manitohensis, 

 from twenty to twenty two radiating raised lines were counted in a corres- 

 ponding space. 



C. J/a iiitobensis is also very closely allied to the C. strialella of Dalman, 

 from the Silurian (Upper Silurian) of Europe, and to the C. llard.rensis 

 of Phillips, from the English Devonian. Of the former it may prove to 

 be a local and stratigraphical variety, and from tlje latter (as described by 

 Davidson) it seems to differ chiefly in the circumstance that its radiating 

 "striie" are not minutely spinose. 



(S.) Productella productoides, var. membranacea. 



Leptd'ita membranacea, Phillips. 1841. Pal. Poss. Cornw., Dev. and W. Somerset, 



p. 60, pi. XXV, iig. 101. 

 Strophaloaia producloide«, (Murchi.son, 1840) Davidson. 186.5. Mon. Brit. Dev. 



Brach., p. 97, pi. xix, figs. 18-21 ; also, this volume, p. 



216, pi. xvi, figs. 1 and 2. 



Monroe Point, Lake Manitoba, J. B. Tyrrell and J. F. Whiteaves, 1888 : 

 six specimens. 



In the first part of the eighth volume of the Palaeontology of the State 

 of New York, just published, (p. .317) Professor Hall follows Professor 

 King in referring the typical form of this species to Productella rather 

 than to Stroplialosia, and this view has been adopted here, as equally 

 applicable to the var. membranacea. 



