Beede.] Carboniferous Invertebrates. 13 



until they had gained some considerable size, as the pores are 

 about equally developed all over them ; they are somewhat 

 globular in form. Where they were abundant, as is generally 

 the case wherever they are found, they soon come in contact 

 with each other and form a solid mass, sometimes appearing to 

 coalesce, but generally in breaking they part along the line of 

 contact, and neither specimen seems to be ruptured. As yet 

 spicules have not been positively made out. There are no sili- 

 ceous spicules, and several thin sections have failed to show 

 any calcareous ones. The absence of siliceous spicules and 

 chert in the specimens, and the absence of chert in the rock, 

 makes it practically certain that they are calcareous sponges. 

 There is on weathered specimens, where the dermal layer has 

 been removed, a peculiar, more or less haphazard arrangement 

 of pits, surrounded by elevations, which is probably caused by 

 an internal calcareous skeleton, composed of fused spicules. 

 The different individuals of this species vary from half an inch 

 to a foot in diameter, but seldom are more than six inches high. 



They are found in abundance in the northwestern part of 

 Atchison, in western Doniphan and eastern Brown counties. It 

 is not uncommon to find them making up a stratum of lime- 

 stone six inches thick. They are confined to a single narrow 

 horizon in the Burlingame shales. 



The cloaca is generally filled with limestone, which, except 

 at the center, is arranged in concentric layers as it was filtered 

 in, giving the cloaca and the parts immediately surrounding it 

 much the appearance of a concretion. 



The sponge evidently belongs to the Pharetrones, and appears 

 most closely related to Corynella and Stellispongia. It differs 

 from the former in not having the cloaca funnel-shaped, and 

 the fact that the cloaca does not terminate below in vertical 

 branching tubes any more than it does above, and possesses no 

 distinct exhalent aperture. It is much more closely related to 

 the latter, but is simple, and appears quite different in its spic- 

 ules, while the cloaca is confined to the base. 



