'^ Tag'' o/Ccelopleurus Maillavdi. 89 



developed in the fossil Coelopleuri of the Tevtiavies of Western 

 India (Pal. Indica, ser. xiv., " Fossil Echinoidea of Sind") ; 

 and in investigating the morphology of the recent Gcelopleurus 

 Maillardi I found evidences of the function of the region. I 

 have not had an opportunity of examining the structures 

 upon any other recent form, and possibly the description now 

 given may stimulate other students of the Echinoidea to add 

 to our knowledge. 



Dr. Giinther was so good as to allow me to study one of 

 the specimens of C Maillardi in the British Museum, and 

 the preparation which forms the subject of this short descrip- 

 tion will shortly be in the possession of the museum. A 

 portion of the test around the peristome was cut away, so as 

 to include a branchial cut and a tag, and the peristomial 

 membrane which is attached to the edges of the test was 

 carefully separated. The piece of test was then placed in 

 nearly absolute alcohol. After the lapse of a few days the 

 tissue on the tag, which was in organic contact with the 

 test beneath, was separated, floated off, and stained with 

 eosin, cleared in oil of cloves, and mounted in balsam. 



The base of the structure is a reticulate, perforate, and 

 more or less broadly spiculate calcareous layer or layers, and 

 the nucleated soft structures environ the hard parts. The 

 surface consists of connective tissue, minute nucleated cells 

 showing evidences of cilia, and extremely fine nerve-filaments. 

 In three places this common ectodermal structure became thick 

 and rose into three small bodies, each of which has a broad 

 base and a surface of digitiform and sometimes ragged pro- 

 cesses. The surface of each of the bodies is highly nucleated, 

 but no trace exists of a central canal, and, indeed, the appear- 

 ance given is that of solidity. 



The three bunches of tissue are eminently branchial in 

 their appearance, and, so far as I know, resemble in their 

 construction the branchiae on the peristomial membrane. Un- 

 fortunately these last structures in Coelopleurus are so covered 

 with pigment bodies — which are not quite absent, moreover, 

 from the bodies on the tags — that a satisfactory preparation of 

 them has yet to be made. 



There does not appear to be any connexion between the 

 bodies on the tag and the water-system of the ambulacra, and 

 probably they act as respiratory organs by increasing the 

 surface of the common derm. 



