390 Herbert L. Hawkins — Studies on the Echinoidea. 



In 1884, in this Magazine, Duncan, to use his own words, 

 " enlarged upon the nature of the peristomial structure of Galerites 

 albogalerus " ( Conulus), and proved, at least to Lis own satisfaction, 

 that neither jaws, teeth, nor perignathie girdle, were developed in 

 that species. To this opinion he and Sladen adhered in 1889. 



During the same period Loven had turned his attention to the 

 perignathie structures of the Holectypoida, and published the 

 results of his researches in 1888 in the course of his paper on 

 the (probably misleading) discovery of Pygastroides relictus. In 

 respect of the perignathie girdle of Discoides, Loven's observations 

 led him to conclusions as to its structure which were diametrically 

 opposed to those of Duncan and Sladen in practically all features of 

 importance. He also expressed the belief that both Discoides and 

 Conulus were furnished with lanterns and teeth. To this Duncan 

 and Sladen replied in 1889 by a regrettably dogmatic paper in which 

 they repeated their previously expressed views, alter the examination 

 of anew series of specimens. Again they stated that the girdle of 

 Discoides was composed wholly of interambulacral structures (ridges) ; 

 that Conulus had no girdle at all, or at most a degenerate and 

 functionless ridge ; that it was extremely improbable that Discoides 

 had any jaws ; and, by inference, that it was practically certain that 

 Conulus was totally devoid of a lantern. In 1892 Loven published 

 a fuller account of the girdles of the two genera, and, either in 

 charity or' sarcasm, referred to the work of the two British authors 

 in a footnote only, without comment. He also had the intense 

 satisfaction of being able to describe the pyramids of the lantern in 

 Discoides. 



Since the period of this somewhat strained, but eminently 

 courteous, controversy, the present writer has published a more 

 complete account of the lantern and teeth of Discoides (1909), and 

 has recorded the discovery of indubitable teeth in Conulus subrotundus 

 (1911). For the rest, the question of the characters of the 

 perignathie girdle in the two genera remains practically in the 

 unsatisfactory condition in which it was left. 



The difference between the two interpretations of the girdle of 

 Discoides can be best understood by a comparison of the figures given 

 by the respective authors. If, following the advice of Duncan, we 

 "very respectfully draw our . . . attention to [Loven's drawing], 

 fig. 2 " (here partly reproduced in outline on PI. XXV, Fig. 2), we find 

 that each sector of the girdle is composed of four vertically elongated 

 plates, the outer pair of which is united to the ambulacra by suture, 

 while the inner pair articulates with three small polygonal plates on 

 the interambulacral margin of the peristome. The outer pair consists 

 of "processes" in Duncan's terminology, while the inner pair, with 

 the three small plates, constitutes the " ridge ". On comparing this 

 drawing with Duncan & Sladen's very diagrammatic sketch (here 

 copied in part, PI. XXV, Fig. 1), the only discrepancies to be noticed 

 are in the absence of the median interambulacral suture and of the 

 small plates, and in the straightness of the sutures at the bases of the 

 processes. (With the position of the ambulacral pores, another 

 point of difference, we are not now concerned.) But the interpretation 



