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XXII. — On a Pj'c- Brachial Stage in the Development of Comatula, and its im- 

 portance in relation to certain Aberrant Forms of Extinct Crinoids. By 

 Professor Allman. (Plate XIII.) 



(Read 16th February 1863.) 



While engaged last autumn in examining with a hand-lens the contents of 

 a phial into which I had transferred some of the refuse of the dredging-boats 

 employed in the oyster fishery on the coast of South Devon, my attention was 

 attracted by a minute organism which adhered to a fragment of one of the larger 

 Sertularidans. Under this low power it resembled somewhat a Campanularia, 

 with the polype expanded ; but, on being removed with a portion of the substance 

 to which it was attached, and placed in a glass trough under the compound 

 microscope, I found that it had closed up, and now resembled in form a cup 

 surmounted by a pyramidal lid, and supported on the summit of a long jointed 

 stem (Plate XIII., fig. 3). After it had remained for some time in this condition, 

 I observed the pyramidal lid begin to open by the separation of its sides, and 

 numerous long flexile appendages to'lssfue^from the cup (figs. 1 and 2). 



I saw that I had now before me a remarkable crinoidal type, likely to be of 

 much significance in its bearing on the general morphology of the order, and 

 more especially interesting, as affording a key to the nature of certain extinct 

 genera of Crinoids. It is the object of this communication to give some account 

 of the points, which a very careful examination has enabled me to make out in 

 the only specimen which I was fortunate enough to obtain. 



For convenience of description, the little Crinoid may be divided into the body 

 and the stem. The body consists of a calyx or cup-like portion, covered by a 

 pyramidal roof The calyx is composed chiefly of five large plates, very distinct, 

 and united to one another by simple suture. Between the lower edge of these 

 plates and the summit of the stem is a narrow zone, in which no distinct indica- 

 tions of a composition out of separate plates can be detected. Between the 

 upper angles of every two contiguous large plates there may, with some care, be 

 made out a minute intercalated plate ; there would thus be five of these little 

 intercalated plates, which, though by no means so evident as the five large 

 plates which alternate with them, are sufficiently so to leave no doubt of their 

 presence. The entire length of the body and stem is about ^vth of an inch, and 

 that of the body alone about g^jth of an inch. 



The pyramidal roof which closes the cup in the contracted state of the 

 animal is composed of five large triangular plates, each supported by its base 

 upon the upper edge of one of the large plates of the calyx, and with the small 

 intercalated plates encroaching upon its basal angles. When the animal is 



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