444 MR. UERBERT L. HAWKINS ON 



Pygaster. He contrasted this family with the Echinoneidse, in 

 which he placed Echinoneics, Pyrina, and several other genera. 

 This was the first time that the presence of jaws was treated as 

 an essential feature in the classification of the group. 



Wright's system of classification wa,s adopted for many years 

 by almost all the Echinologists who dealt with the group, although 

 slight changes in the generic personnel of the Echinoconidse were 

 inti-oduced. Cotteau (28) removed Hyhoclypus, with good reason, 

 from the family, and added the genera (unknown to Wright in 

 1856) Ano7-thopygus and Pileus. 



The compact group thus determined, bound together by the 

 characters of a short and accurate diagnosis, became generally 

 accepted. Loven (31) worked on this classification as a basis, and 

 Wright (32) agreed with Cotteau's modifications. Perhaps no 

 surer indication of the natural character of the grouping could 

 anywhere be found than in the fact that Pomel (37) was unable 

 to find any cause for more than intei-nal changes in the family. 



With a subordinal rank within the group of Gnathostomes 

 Clipeiformes, Pomel placed the section Galerides. This section 

 he subdivided into two chief families, the Echinoconides and the 

 Pileides. The latter family was further separated into two sub- 

 families, the Discoidiens and the Pygasteriens. Although many 

 new " genei'ic " terms were introduced, no forms were included 

 among the Galerides that were not previously classed with the 

 Echinoconida3. The separation of the PJchinoconus-grouTp from 

 the other genera was natural. In the Pileides, the first group 

 was simply the original genus Discoidea of Agai>siz in a dis- 

 membered state, while the second group included the same author's 

 early conception of the genus Pygaster. The clfxssification of 

 Pomel was therefore, in this group, quite orthodox, a condition of 

 aifairs sufficiently surprising in view of the great changes he 

 proposed in the arrangement of many of the other groups. 



In 1889, Duncan (44), who expressly dissociated himself from 

 Pomel's views of the relative importance in classification of 

 various structures, published the invaluable Revision of the 

 Genera, etc. of Echinoidea. In this work, he realised the great 

 importance of the Holectypoida as an annectant group. So 

 thoroughly intermediate in its characters was the group that he 

 definitely stated that his classification was artificial, and as such 

 tentative. The Holectypoida received the rank of an Order, 

 equivalent in importance to the Clypeastroida or the miich larger 

 groups of the Diademoida and Spatangoida. 



It was chiefly on the peristomial and jaw-structures that 

 Duncan classified the group, and on that account it was particularly 

 unfortunate that he should have had such a fixed belief in the 

 absence of jaws in some genera in which they have since been 

 discovered. Curiously enough, although, in the same year as the 

 publication of the Revision, he definitely stated his disbelief in 

 the existence of jaws in Discoidea (45), he allowed that genus to 



