392 On CalamojwrcB in gravel deposits near Ann Arbor, Mich. 



The organization of tlie animal does not seem to have been 

 such as to determine, by a sort of mathematical necessity, the po- 

 sition of the pores ; on the contrary, it appears that tlie animal 

 was at perfect liberty to leave ad libitum such openings in its 



Calamopora favosa Goldfuss, Tab. 26, f. 2. 



d by 

 fith those found here, is always connected with some 

 difficulty, but, in this case, the fossil itself is of American origin, 

 and so, lay looking over the specimens from the locaHty indicated 

 (Dmmmond's Island), Calamopora favosa can easily be pointed 

 out. According to Goldfuss's figure its tubes are a little over 3 

 millimeters wide, and in his rather short description he desig- 

 nates convex diaphragms and two opposite rows of pores on 

 each side as the distinguishing characters of it. It will not 

 appear superfluous, to add to this some more special observa- 

 tions. The tubes, which in a given specimen are all of similar 

 size, have a very variable diameter, between the extremes of 4 

 millimeters and 1|- millimeter; for example I observed a tube 

 measuring 9 millimeters in one specimen, the tubes of which had 

 an average size of 4 millimeters. The inner side of the tubes is 

 densely covered with spinules, some of which are bifurcated, and 

 which also extend over the upper face of the diaphragms. 



The spinules are placed in about 12 longitudinal rows, sepa- 

 rated by as many longitudinal sulci, and a transverse order also, 

 corresponding with the lines of growth seen on the outside, can 

 be noticed in the arrangement of the spinules. 



Under the magnifier this position of the spinules in rows is 

 not so obvious as with the naked eye, as they appear then more 

 irregularly dispersed. Pores of moderate size are disposed over 

 the sides in 1, 2, or 3 irregular rows, but not as Goldfuss asserts, 

 in pairs; pores placed in pairs are sometimes seen, but this is 

 by no means the rule. 



The diaphragms are subject to many variations, some are almost 

 flat, others form a high, rounded or transversely elongated 

 cone, the top of which is oflen deeply impressed ; this impres- 

 sion protrudes on the lower side as a rounded elevation, of which 

 Goldfuss gives a good representation, Tab. 26 fig. 2, 6. Some- 

 times in the centre of tliis depression a hole is left open, or it is 

 found closed up subsequently with a solid globular piece. 



Marginal depressions in the diaphragms, similar to those fig- 

 ured by Goldfuss in his Calamopora alveolaris, are seen in difler- 

 ent degrees of development. Sometimes they are hardly to be 



" ced, at others thev becor 



' become large and give the end 

 the diaphragma, but often 



starHke appearance. Frequently 12 such dfepressions encirc 

 ' Q less. 



