216 ROYAL SOCIETY OF CANADA 



3. OrtJiis (Rhipidoviella) , cf. oblata, Hall. 



A single imperfect specimein is referred to this species. It is about 

 31 mm. wide and 10 mm. deep. The valve is nearly flat along the middle 

 part of the shelly, the other valve gently arching and it agrees in surface, 

 and surface markings with specimens of Orthis oblaia of the Lower 

 Helderberg. It is to be noted^ however, that a very closely related form 

 is cited by Hall from the Comiferous of Western New York under the 

 name " Orthis sp. ? ^ also Ortlm alsus of the Schoharie grit presents 

 characters of the species 0. ohlata, Hall (see p. 37). The conclusion is 

 therefore reached that we have here a representative of the subgenus 

 Rhipidomella in the fauna, but the evidence as to its particular stage of 

 mutation is wanting. 



4. Orthis (Dalmanella) , suhcarinata. Hall. 



A 'single, decorticated pedicle valve, presents closely the characters 

 expressed in Hall's figure d of Plate XII, of Orthis subcarinata. Tlie 

 greatest width above the middle is 18.4 mm., the length 15 mm. Here 

 also we note close resemblance of the Lower Helderberg species to a 

 species (0. lenticularis var.) of the Corniferous limestone of Western 

 New York. 



5. Orthis (Dalmanella), cf. quadrans. Hall. 



A small quadrate Orthis is referred to this species. It is I214 mm. 

 wide, quadrate in form with j-ather strong median sinus and the cardinal 

 quarter of the 'shell slopes abruptly toward the edge. This reference 

 cannot be taken as positively expressive of Lower Helderberg age, since 

 the form is similar to the Corniferous form 0. lenticularis-lentiformis, 

 Hall, and both of them, evolutionally, must be regarded as closely related 

 to the typical 0. suhcarinatus of the Helderbergian fauna. 



'The evidence furnished by these several specimens of Orthids in the 

 fauna is not conclusive as to their age, tho" it may be regarded as signi- 

 cant of closer affinity with the fauna of lots 2 and 3, in which the 

 Orthids are abundant, than with the Hamilton, the Orthids of which are 

 also abundant but have a different expression. 



6. Leptœn-a rhonihoidaUs. }yilcl-ens. 



This species is represented, but as the specific characters are both 

 variable and of wide geologic range, the mere presence of the species is 

 not significant of any limited horizon within its wide range. 



1 Pal. N. Y., part I. 1867, p. 40. 



