CRYPTOSTOMATA. 55 
Fairiily IPTII^OI^IC'TYOIN'IID^E: TTli*icH. 
Genus PH^NOPORA Hall. 
Distinguished from Ptilodictya by the presence of two or more mesopores in each inter- 
space between the ends of the apertures. 
PlIJiNOPORA ENSIFORMIS Hall. 
PI. XXVII, figs. 8, 9. 
Phsenopora ensiformis Hall, Nat. Hist. New York, Pal. II, 1852, p. 48, pi. 18, figs. 8a-c. 
Phsenopora ensiformis Nicholson and Hinde, Canadian Journal, new ser., XIV, 1874, p. 142. 
Phsenopora ensiformis Nicholson, Pal. Province Ontario, 1875, p. 45, figs. 19, 2, 2a. 
Ptilodictya ensiformis Ulrieh, .Jour. Cincinnati Soc. Nat. Hist., V, 1882, p; 172. 
Phsenopora ensiformis Foerste, Geol. Survey, Ohio, VII, 1895, p. 598. 
A narrow, unbranched species of Phsenopora occurs not uncommonly at most of the 
Rochester shale localities and agrees in all respects with the Clinton form described by Hall 
as Phsenopora ensiformis. In this form the characteristic mesopores occupying the inter- 
spaces between the ends of the aperture are often made out with difficulty and this faci 
causes the zoarium to resemble Ptilodictya very closely. Upon close examination, however, 
or by means of thin sections, two small mesopores may be found occupying the position 
normal for Phsenopora. 
The zoarium, which is bifoliate and pointed at the base for articulation, averages 25 mm. 
in length and 2 mm. in width; each face bears from 7 to 1 1 parallel rows of zooecia; 6 zocecia 
in 2 nun. measured longitudinally; apertures in linear series between slightly raised longitu- 
dinal lines, quadrangular, measuring about 0.18 nun. by 0.30 mm., but in marginal series, 
oval slight ly oblique and larger than in the middle ranges. 
Occurrence . — Abundanl in the Clinton rocks of western New York and Ontario, and not 
uncommon in the Rochester shale of the same region. Rare in the Clinton rocks of Ohio 
and also in the Osgood beds at Osgood, Ind. 
Catalogue number, 35752, U. S. National Museum. 
PlIiENOPORA FIMBRIATA \ ai\ CANADENSIS U. \ai\ 
PI. XXI, figs. 17 -19. 
Compare Phsenopora fimbriata (.lames) Foerste, Bull. Sei. Lab. Dtenison Univ., 11,1887, p. 161; ibid., 
Ill, L888, pl.*15, fig. 7. 
The form for which the above varietal name is proposed agrees in method of growth with 
the characteristic Ohio Clinton species Phsenopora fimbriata, but differs in the following 
respects. First the zocecia of the variety are smaller, 8 occurring in 2 mm., measuring 
lengthwise, while only 6 are found in the same space in the Clinton form. Second, the walls 
of the variety are considerably thinner while the mesopores are small and inconspicuous. 
While the thin walls and small, inconspicuous mesopores of the variety may be due to a 
youthful stage of growth in the specimens studied, yet the smaller zooecia seem to be of 
sufficient importance to designate the Rochester shale form as a good variety if not a species. 
Occurrence. — Rochester shale, Lockport, N. Y., and Grimsby, Ontario. 
Catalogue numbers, 35753, 44148, U. S. National Museum. 
