NO. 1192. TRENTON FAUNA OF BAFFIN LAND— SCHVCEERT. 161 



CTENODONTA BAFFINENSIS, new species (Ulrich). 

 (Plate XIII, figs. 7-10.) 



There is but a single example of this species present, and this was 

 provisionally identified as G. scojieldi Ulrich.' The author of the species 

 writes that, while it has the general aspect of C. scojieldi, it is neverthe- 

 less sufficiently distinct to be recognized as new. Mr. Ulrich has made 

 the following comparisons: 



At first sight this is extremely like C. scojieldi, but ou closer inspection, and par- 

 ticularly when compared with the types of that species, certain peculiarities become 

 so prominent that I wonder that they were not observed at once. The first of these 

 is a depression, or rather widening furrow, extending vertically from the beaks across 

 the valves. This is sufficient to cause a straightening, even a slight concavity, in 

 the ventral outline. The outline of the valves differs further in the postventral 

 (wider) region being more prominent and more narrowly rounded here. In a car- 

 dinal view the species agrees best with C. scojieldi, but in a lateral view the outline 

 corresponds better with C. medialis and C. nitida Ulrich. The contour of the valves, 

 however, shows it to be a distinct form, the mesial depression possibly indicating 

 relations to species of the type C. carinata Ulrich. C. scojieldi also has no radiating 

 lines; the concentric lines are equally as delicate. 



Collector. — E. W. Porter. The type is in the American Museum of 

 Natural History. 



CTENODONTA FROBISHERENSIS, new species. 

 (Plate XIII, figs. 11-14.) 



Of this little shell there are two well-preserved specimens, which 

 appear to be distinct from all other Ordovician Ctenodontas. Probably 

 the species most nearly related is C. albertina Ulrich,- from which it 

 differs in having the beaks more centrally situated, the valves shallower, 

 and in being less drawn out anteriorly. At first this form was thought 

 to be most closely related to C. oviformis Ulrich,^ but the author of 

 the latter species writes that the Arctic shell "has different propor- 

 tions" and that it represents a new species, C. oviformis is less high, 

 has narrowly rounded ends, and the beaks are situated nearer the mid- 

 length. Its rounded-ovate form distinguishes it from the other Fro- 

 bisher Bay species, all of which are nasute forms. 



Collectors. — J. N. Carpender and A. V. Shaw. Oat. No. 28165, 

 U.S.N.M. 



Family MODIOLOPSID^ Ulrich. 



MODIOLODON ARCTICUS, new species. 



(Plate XIII, figs. 18, 19.) 



There is a good cast of the interior of the valves of this shell in the 

 present collection. The species is very much like 31. patulus Ulrich,^ 



iGeoI. Minn., Ill, Pt. 2, 1894, p. 593, pi. XLii, figs. 53-58. 



2 Ibidem, p. 598, pi. XLii, figs. 76-82. 



3 Ibidem, p. 586, pi. XLii, fig. 29. 



■* Ibidem, p. 521, pi. xxxvii, figs. 20-24. 



Proc. N. M. vol. xxii 11 



