NARRATIVE OF THE CRUISE. 313 



"Like all the deep-sea Comatulse, it is of very small size. As in Eudiocrinus there 

 are five undivided arms, but they are unfortunately broken off quite short. The radials 

 which bear them are not, however, in contact either with the centro-dorsal or with one 

 another, for they rest on a ring of five basal plates, which alternate with them in 

 position (fig. 124a, b). There is only one other genus of" recent Comatuke (Atelecrinus) in 

 which this is the case ; but there is no Neocrinoid, either recent or fossil, in which the 

 radials do not meet one another laterally, and form a closed ring. In Thaumatocrinus, 

 however, every two radials are separated by an interradial plate, which rests on a basal 

 (fig. 124a, b, i). This is a character which is limited to certain Palaeozoic Crinoids belong- 

 ing to the family Rhodocrinidse. One of these interradials in Thaumatocrinus, that on 

 the anal side, bears a short and tapering jointed appendage, which looks somewhat like an 

 undeveloped arm (fig. 124a, b, aa) ; and it is only in some of the Palseocrinoids, e.g., 

 Reteocrinus, Taxocrinus, and Onychocrinus, which reach back to the Lower Silurian 

 period, that any similar structure is to be found. . 



" Besides reproducing these singular characters of long extinct Palseocrinoids, Thauma- 

 tocrinus presents another structural feature, which is peculiar to itself among Comatulse, 

 although appearing in the stalked Rhizocrinus and Hyocrinus, viz., the existence of a 

 pyramid of oral plates protecting the mouth (fig. 124b, o). 



" The combination of these various characters in an abyssal Crinoid, which is not 

 stalked, however, but belongs to the specialised Comatula-type, is a point of very 

 considerable interest ; and, in my opinion, Thaumatocrinus is by far the most remark- 

 able of all the Crinoids obtained by any of the recent deep-sea exploring expedi- 

 tions." 



The Myzostomida.- — " On some specimens of Hyocrinus and Bathycrinus which were 

 dredged at Stations 146 and 147 from depths of 1375 and 1G00 fathoms, Dr v. Willemoes 

 Suhm discovered a remarkable species of Myzostomida (fig. 126e) which constitutes an 

 entirely new group of these Crinoid parasites. 



" These specimens and the other Myzostomida collected during the voyage, 1 together 

 with material subsequently transmitted to him by Dr. P. H. Carpenter, have enabled 

 Professor v. Graff to throw a new light upon the structure and mode of life of these 

 animals. 



" The accompanying diagram (fig. 125) displays the structure of the Myzostomida in so 

 far as it was known before the publication of Professor v. Graff's Report. The typical 

 Myzostoma is a disk-shaped, bilaterally symmetrical, unsegmented animal of from 

 - 5 mm. to 1 cm. in diameter; it possesses five pairs of unsegmented parapodia, and four 

 pairs of suckers both situated upon the ventral surface ; upon the margin of the body 



1 At Stations 146, 147, 170, 174, 186, 187, 190, 192, and 214. 

 (narb. chall. exp. — vol. i. — 1884.) 40 



