﻿July, 1857.] 



ELLIOTT SOCIETY. 



233 



these remarks, suggested itself to Mr. McCrady immediately on 

 the examination of this specimen, which unfortunately, he had 

 only seen this once, and then for scarcely ten minutes. It con- 

 sisted of an even number of rods diverging from a central space, 

 about which they were not disposed at equal distances asunder, 

 but symmetrically, and bilaterally, so that there were two sides 

 to the specimen. Between these rods was the impression of the 

 soft parts curving inwards. The only illustrations of a similar 

 object known to Mr. McCrady, were the figures of Muller, of the 

 upper view of the larvae of some Echinoderms. (See Ophiuren- 

 larven PL 1, fig. 4.) And it immediately occurred to him that this 

 specimen was the upper view of a Pluteus-like animal, which had 

 been subjected to pressure from above, while resting in a vertical 

 position. It appeared to Mr. McCrady that no other explanation 

 of this specimen, so far as his opportunities had extended, could 

 be made. 



During the same year, Mr. McCrady had been shown by Prof. 

 Hall, while in Boston, some Graptolites from the west These had 

 the stem very much expanded, and were immediately explicable, 

 by comparison with the expanded portion of the shafts in Mulier's 

 PL 7, fig. 4, 4, Siebente Abhandlung. With regard to the long 

 Graptolites, they are usually solid, and sometimes serrated on one 

 side only, sometimes on two; they are, also, though rarely, yet 

 sometimes divaricate. All these characteristics would be explain- 

 ed by a comparison with the long shafts of the tent-frame in Plu- 

 teus. They, also, usually terminate abruptJy, and are generally 

 presented in fragments, and this is consistent with the case of Plu- 

 teus and the larvoe of Echini, in both which, also, the rods are 

 very fragile and easily broken. 



The dissepimental fragments were also explicable by comparison 

 with the longer rods of the larva? of Echini proper. If Mr. 

 McCrady's suggestion was correct, it was also probable that smooth 

 unserrate Graptolites would be found corresponding to the smooth 

 rods in the larvas of Echinoderms. 



There were certain apparent difficulties which might be urged 

 in opposition to this, which Mr. McCrady desired to notice. Such 

 was the external cortical horny sheath, which in Graptolites, usually 

 surrounded the calcareous rods. This might have been the modi- 

 fied remains of the external soft tissues of the Pluteus-like animals 

 surrounding the rods and shrinking upon them at the death of the 

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