NIAGAKA GROUP. 



209 



In the description of the fingers and tentacula, it was remarked that they appear to be 

 anchylosed together, and the same is often true of the joints of the fingers themselves. In a 

 single weathered fragment, I have been able to discover more fully the articulation of the ten- 

 tacula to the joints of the fingers, and even the joints of the tentacula themselves. The latter 

 are quadrangular, oblong, their length being twice or thrice their vertical extent or thickness ; 

 there are about twenty joints in each tentaculum near the base, and six or seven near the sum- 

 mit ; they are closely arranged, and, in freshly broken specimens, anchylosed so firmly that the 

 surface presents the appearance of a solid striated plate as in fig. 3 d, the striae indicating the 

 direction of the tentacula. 



It has been remarked that the elongated subconical plate between the arms of each pair is 

 sometimes truncated below, by resting on the scapular plate : this character is variable, and 

 sometimes it occurs in one, two, or three plates of an individual ; it can not, therefore, be re- 

 lied upon for indicating a specific distinction. 



Fig. 1. An individual with lower portion of the cup broken off; the upper part, from the com- 

 mencement of the arms, having a conical form surmounted by the short proboscis. 



Fig. 2 a. An individual retaining a portion of the column, and having the summit somewhat 

 spreading, probably from compression. One or two of the lower ranges of plates of 

 the proboscis are still preserved ; the upper part being broken off, shows the opening 

 into the alimentary canal. The entire specimen is somewhat compressed, and adheres 

 to a slab of shale. The exposed face shows two of the subconical plates, between the 

 arms of the same pair, truncated at base. 



Fig. 2 b, A young specimen having the same characters as the preceding. 



Fig. 2 c. The structure of the species as shown in the preceding and other specimens. The large 

 ten-sided plate is marked F, as a costal plate ; while the smaller plate, directly 

 above the pelvic plate, is marked G, as an intercostal plate* (see description and 

 remarks). 



Fig. 2 d. K fragment of one of the fingers, showing the articulation of the tentacula, and their 

 direction inward and upward. 



Fig. 2 e. A fragment of a column, showing the alternating larger and smaller joints. 



Fig. 2 /. Transverse section, showing the pentapetalous canal. The fragment figured is worn, 

 and does not show the deep striae. 



Fig. 2 ^. A fragment from the column of 2 6 enlarged. 



Fig. 2 A. A fragment of a very minute column. 



Fig. 3. Those with ovoid forms, or rounded summits. 

 Fig. 3 a. Vertical view of a fragment, looking upon the summit, showing the convergence of 

 the fingers, and the union of the interstitial ribs around the canal, which penetrates 

 thence to the cavity below. The proboscis is broken off. 



* There are some errors in the arrangement of the letters in the higher plates, which may be corrected thus : The 

 letters K and M are affixed to the two pairs of arm-plates, each of which should be marked K. The plates marked N 

 should be marked M, and N affixed to the succeeding portion, implying the fingers which at the summit are indicated 

 by the letters c, c. 



[ PALiEONTOLOGY VoL. II.] 27 



