INVERTEBRATES. 221 



organs (see * of cut B, fig. 19), having much the delicacy and appearance of 

 tentacles. 



In the above cut, the minute true arms of the typical species of Goniasteroidu- 

 crinus, are seen to branch so as to form nine to each ray. The cut shows only 

 their outside, in which we have seen no indications of ambulacral furrows; but 

 these may have been obliterated in cleaning the specimen, or possibly they may 

 present the anomalous character of being on the under side, and thus differ 

 from those of all other known crinoids. As far as these arms can be traced 

 near the base, they are each composed of a single series of minute pieces, but 

 according to Mr. Lyon, they are farther down, composed each of a double 

 series of minute interlocking pieces. 



These true arms connect with the body at the openings that suggested to 

 Prof. Hall the later name Trematoerinus for this group. Such differences as 

 these, in the parts connected with the reproductive, and perhaps the respira- 

 tory organs, should surely separate this type from Rhodocrinus. 



But as these organs have not yet been seen entire, in the typical European 

 species of the genus Gfilbertsocrinw, it may be argued that we have no right to 

 conclude that the Goniasteroidocriuus group is congeneric with Phillips's genus. 

 "We think, however, that any one who will take the trouble to compare the 

 foregoing cuts of Goniasteroidocriuus tuberosus and our figure of G. fiscellus, on 

 pi. 15, fig. 5, together with the other American species described by Prof. Hall 

 under the name Trematoerinus, with Phillips's figures of his typical species of 

 Gilbcrtsocrinus, and particularly with Cumberland's figures of one of the same 

 species, which we have reproduced for comparison, on page 217, will agree 

 with us that these European species must have had these organs, with the 

 slight difference of relative position already mentioned, exactly as in Goniaste- 

 roidocrinus* Nor can we believe the difference in the position of the false 

 arms, with relation to the true ones, alluded to above, of more than subgeneric 

 importance. 



The fact that Cumberland had, in 1826, proposed the name Ollacrinus for 

 Phillips's typical species, leaves us in some doubt whether we should not adopt 

 his name for the genus, in accordance with the rules of priority. The reasons 

 for doubting the propriety of adopting his name are not only that he gave no 

 diagnosis or description either of his typical species or of the genus Ollacrinus, 



* It is due to Mr. Billings that we should state here, that so far as w.e know, he was 

 the first author who called attention to these two sets of appendages in Gilbertsocrinus 

 bursa, Phillips (Decade Hi, Canadian Organic Remains, p. 25 and 26), though, owing 

 to the fact that he had never seen an entire specimen, he there seems to have regarded 

 this as the structure of Rhodocrinus. We are gratified to be able to state, however, 

 that he now fully concurs with us in the opinion that Gilbcrtsocrinus is distinct from 

 Rhodocrinus proper. 



