Hambach — Revision of the Blastoideae. 19 



in their collapsed state the supplementary poral pieces of Dr. 

 Roemer * or outer side plates of later authors. f 



What could be the function of these supplementary poral 

 pieces situated as described by Dr. Roemer, within the poral 

 opening? As I understand the term it applies to something 

 similar to and in addition to the poral piece, that is a small 

 piece inserted in the poral opening. According to the Doc- 

 tor's description it served to reduce the opening, which, how- 

 ever, is not a very plausible supposition, as the same result 

 might have been accomplished by nature in a much simpler 

 manner by lessening the groove in the pore piece. Therefore 

 I deem it proper to seek for another explanation which is to 

 be found in supposing them to be tentacles. The correctness 

 of this supposition is easily tested, as there can be only three 

 possible conditions : — 



1st. If a supplementary poral piece existed 

 it should be found by making a transverse sec- 

 tion through or near the middle of a pore channel, <t- 

 say at the line indicated from a to b in Fig. 10. 



2d. If then the supplementary poral pieces ^^^- ^^• 

 are not preserved, we should find the poral opening vacant or 

 filled with foreign matter. 



3d. If my supposition is correct and the tentacles are pre- 

 served, we will find them by making such a section, in either 

 an open or collapsed condition. In a number of sections I 

 have made I can prove the existence of the so much doubted 

 tentacles in either condition. Fig. 1, Plate II., is a trans- 

 verse section through a row of poral pieces of Pentremites 

 Jlorealis, showing the preservation of the tentacles in a some 

 what collapsed condition. Fig. 4 is a similar section of JPen- 

 tremites abbreviatus showing the tentacles in an open condition. 

 I could show further evidence of their existence in pathologic 

 specimens where mechanical injuries had been inflicted, caus- 

 ing a hypertrophic growth of some of the tentacles into a little 

 bundle of tubes. 



The plications, as already stated, vary in number and in the 



* Wiegmann's Archiv fiir Naturgeschichte, Jahrg. XVII., Bd. I,, p. 335, 

 t Eastman. Text Book of Palaeontology, Vol. I., p. 191. 



