290 THE PALEONTOLOGY OE MINNESOTA. 



[Batostoma fertile . 



latter, I am now fully satisfied, embraces the progenitors of Trematopora, and as the 

 relationship seems to be very intimate it may be well to consider the advisability 

 of dropping Batostoma in favor of Hall's older name. The Calloporidce, with Aspi- 

 dopora removed to the Monticuliporidce, might be united with the Diplotrypidce, from 

 which, in that case, it would be well to remove Batostoma* But for the reasons 

 stated it was deemed inexpedient to carry out sweeping innovations in the present 

 work, and the only excuse for their mention here is that it seemed necessary to 

 publish some idea of the lines in which progressing knowledge is likely to modify 

 the present classification. Perhaps also to show how well we are acquainted with 

 its imperfections. 



Batostoma fertile TJlrich. 



PLATE XXV, FIGS. 1-11. 



Batostoma fertile Ulbich, 1886. Fourteenth Ann. Rep. Geol. Nat. Hist. Surv. Minn., p. 92, 



Zoarium attaining a large size, 50 to 100 mm. in hight, consisting of strong, 

 irregularly thickened, more or less compressed branches that divide without regu- 

 larity; thickness of branches 5 to 25 mm., width 8 tp 30 mm. Zocecial apertures 

 varying according to the size and number of the mesopores and the thickness of the 

 walls, from polygonal to circular. In some specimens and portions of others meso- 

 pores are exceedingly few and the zocecial walls thin and generally in contact at all 

 sides; in the majority of examples mesopores are moderately abundant and the 

 walls thicker, but the zocecial apertures are still polygonal or at any rate most of 

 them subangular. From this, the typical form, we can trace the variations by small 

 degrees into a form which, for the sake of reference, may be designated as var. 

 circulare. In this the zocecial apertures are almost perfectly circular, enclosed by a 

 raised rim or peristome, and largely separated from each other by depressed inter- 

 spaces. Often the peristomes are thicker and more distinctly separated from each 

 other than is shown in fig. 6. Interspaces occupied by mesopores varying consider- 

 ably in size and shape. Their mouths are commonly closed by a calcareous plate in 

 which a variously situated rounded opening may be observed. When the preserva- 

 tion is unusually favorable the surface of the plate is studded with very minute 

 papillae representing the terminations of exceedingly small foramina. Acanthopores 

 between one and two to each zooecium, but very small and only in rare instances 

 distinguishable at the surface.- At intervals of 3 or 4 mm. occur clusters of zooecia 

 a little larger than the average, and in the center of these usually small substellate 

 maculae. Between eight and nine of the average zooecia in 3 mm. 



*Tlie families reconstructed in accordance with the above suggestions would be as follows: Cali.opobid.s;, CaUopora, 

 Diplotrypa, Monotrypa, ? Calloporella; Trematoporid^, Trematopora, BatostomaJ Hemiphragma, ? Stromaiotrypa; Ookstellau- 

 ID.E, Gonstellaria, Stellipora, Ificholsondla, t Idioh-ypa. 



