C timings — Development of some Paleozoic Bryozoa. 73 



In Polypora as in Fenestella a 'partial or asymmetrical 

 development of the metanepiasty may give rise to flabellate 

 forms, and by reversal of curvature an occasional cone may 

 arise in either genus, with the zocecia on the surface opposite 

 the usual one, i. e.* the zoarium may turn inside out. Such 

 variations in no way modify the fundamental type. 



Notwithstanding, therefore, the insistence with which 

 authors have proclaimed the intimate connection between 

 Polypora and Fenestella, such supposed close relationship is 

 only another case of morphological equivalence. Waagen and 

 Pichl's 48 erection of subfamilies for the reception of these 

 respective types is more than justified by unmistakable evi- 



4 mm. 



Figures 78-80. — Initial zocecia of Paleschara from the Lower Helder- 

 berg (Shaly) limestone of Indian Ladder, N. Y. Black = protcecium ; cross- 

 hatched (1 to 8) = primary buds ; cross-lined = interstitial buds of a later 

 generation. 1, 2, and 3 are in immediate contact "with the protcecium. 



79-80. Lower surface of the colony ; 78. Upper surface. The primary zocecia 

 diverge rapidly in passing to the upper surface. 



Figures 78, 79 x 8 ; figure 80 x 32.* 



dence, of the existence of which those authors were, however, 

 entirely ignorant. Fenestella and Polypora, as now consti- 

 tuted, comprise a heterogeneous assortment of forms, partly 

 belonging to outside genera and partly entitled to remain 

 where they are. When the correct generic relationships of 

 these forms are determined, the proper arrangement of genera 

 will be to place all forms having the nepiastic stages as in 

 Fenestella in the family Fenestellidce, and all forms having 

 the nepiastic stages as in Polypora in the family Polyporidce. 

 Thamniscus will not belong to either of these families. The 

 position of the other geuera now referred to the family Fen- 

 estellidae as at present constituted, can be determined by an 

 investigation of their development. The writer does not ven- 

 ture an opinion beyond the limits of the types already so 



* The numbers 1, 2, 3, etc., in these figures are not intended to indicate 

 the order of budding. 



