JAMES TYPES OF BRYOZOA—BASSLER. 49 



PRASOPORA HOSPITALIS (Nicholson). 



Plate VII, tigs. 1-3. 

 Monticulipora {Prasopora) selwynii var. hospitnlis Nicholson, Genus Monticnli- 



pora, 1881, p. 209, fig. 45. 

 Monticidipora {Hetcrotrypa) ivinclwlli Jajiks, Paleontologist, No. H, 1882, p. 48; 



No. 7, 1883, pi. I, fig. 5. 

 Monticuliponi luincheUi J. F. .Iamks, Jour. Cincinnati Soc. Nat. Hist., XVIIl, 



1895, p. 87. 



An example of the t3^pe specimen tig-iired by James shows that 

 MonticuUj)ora {Heterotrypci) wliiehelU is the same as the common Rich- 

 mond form, Prasopora liospitallH (Nicholson). In the original descrip- 

 tion eJames compares his species with Nicholson's, but states that the 

 internal structure is vxry different. The tabulation of the zooecia as 

 shown in the slide studied by James (see Plate VII, tig. 1) does appear 

 different from that found in P. hospitalh, but this appearance is 

 largely due to an error in the preparation of the thin section. The 

 zooecial tubes of P. hospitalism when properly sectioned are always 

 lined by c3^stiphragms. In James's section of P. ivinchelUm how- 

 ever, although it exhibits all the other characters of P. /wspitalis, the 

 tabulation appears as though not including true c}' stiphragms but to 

 consist entirely of merely more or less curved diaphragms. The 

 originally sectioned specimen, as proved by a section prepared by the 

 writer, contains an abundance of true cj'stiphragms, and thus is shown 

 to be a normal example of P. /lospitalis in exery respect. That 

 James's section appears to show a different tj'pe of tabulation is 

 believed to result from the fact that it divided the zoarium in a direc- 

 tion parallel with, instead of at right angles to, its growing edge. On 

 reflection it is apparent that species such as this in which the zooecia 

 radiate from the center toward the growing edge will exhibit their 

 normal internal characters best in vertical sections taken along such a 

 radius; or, in other words, at right angles to the growing edge. Thus 

 the cystiphragms of a species will generally appear as nearly straight 

 or more or less curved diaphragms in a section cutting them in a 

 direction opposite to their radial arrangement. Furthermore, it is a 

 fact that James's section was taken from the thin outer edge of the 

 zoarium and therefore exhibits onlj^ an immature condition of the 

 zooecial tubes. In nearly all Montlcullporidai the cystiphragms in the 

 basal part of the zoarium are much larger and extend much farther 

 toward the opposite side of the tube than they do in later stages of 

 growth. Hence, in an improperly prepared vertical section of the 

 immature region, the appearance presented by the cystiphragms is 

 likely to be, as in James's section, that of merely curved diaphragms. 



The massive growth, numerous and closely tabulated mesopores, 

 strong acanthopores, and rounded zocecia with both cystiphragms and 

 Proc. N. M. vol. XXX— 06 4 



