48 PROCEEDINGS OF THE NATIONAL MUSEUM. 



PRASOPORA FALESI (James). 



Plate I, tigs. 1-4. 



Monticulipora falesi James, Jour. Cincinnati Soc. Nat. Hist., VII, 1884, p. ItJS, 

 pi. VII, figs. 2-2d. — James and James, Jour. Cincinnati Soc. Nat. Hist., X, 

 1888, p. 168.— J. F. James, Jour. Cincinnati Soc. Nat. Hist., XVI, 1894, 

 p. 185. 



The character relied upon 1)y the author for distinguishing this 

 species was the presence of a conical, sharp-pointed groove extending 

 across the undej" surface. Any student of the bryozoa knows, or 

 ought to know, that the shape of the excavation left by the object 

 upon which zoarial growth commenced, is certainly not a specific 

 character. The same species may select indiscriminately 'A,ny foreign 

 object such as a mollusk, brachiopod, or another bryozoan to com- 

 mence its zoarial growth. The specimens distinguished by James as 

 M. f>ilesl selected some conical shell such as IlyoUthes or the tapering 

 end of a cephalopod, the impressions left of the shell after its removal 

 not permitting of accurate determination. An examination of the 

 types — the three specimens figured in 1884 — shows that two distinct 

 species are represented. Inasmuch as one of these is new, James\s 

 specific name is here adopted for this form. The original of fig. 2 of 

 the article cited above (1884) is a small but typical specimen of Pram- 

 pora simulatrix Ulrich,'' while figs. 2a-2d represent young examples of 

 a species differing from P. simulatri.r.^ notably in having acanthopores 

 and smaller zo(jecia. 



Comparing P. falesi and /\ smmlatrix the following differences are 

 tioted. In growth the latter rises into dome-shaped or petasiform 

 masses usually 40 or 50 mm. in diameter, and witii a concave base 

 lined by a concentrically wrinkled epitheca, while mature specimens 

 of the former are rounded or irregularly hemispherical in shape, sel- 

 dom over 20 mm. in diameter, and do not show such a well-marked 

 epitheca. P. simulatrix has about 7 of the ordinary zooecia in 2 nmi., 

 while I*, falesi shows 8 to 8t in the same space. Vertical sections 

 bring out especiall}' the small acanthopores of J*, /(tlesi^ but in P. 

 siianlatrix these structures are absent. The tabulation and number 

 and distribution of the mesopores is nuich alike in the two species, 

 but the difference in growth, size of zocecia, and the development of 

 acanthopores in one, makes their separation comparatively eas}'. 



Occwreiice. — Very abundant in the Lexington limestone of the 

 Trenton, in the vicinity of Danville, Kentucky. James records the 

 horizon as about that of the tops of the hills at Cincinnati, but this is 

 un(loul)tedly an (>rror, as his type specimens correspond exactl}' with 

 other examples of the species found in the Trenton at Danville. 



« Fourteenth Ann. Rep. Oeol. and Nat. Hist. Surv. Minnesota, 188(i, p. 85. 



