I'EKONELLA. 51 



1 ays equal stress on their number. Aside from the position of the genital pores, 

 the position of the periproct and the size and form of the petals seem to be the 

 most important specific characters. Whether the plates which cover the peri- 

 proct carry spines (miliaries) or not is also a character of some importance, and 

 the form of the test and the thickness of its margins are also of value. In the 

 Revision, Mr. Agassiz gives four species of Peronella but one of these (rostrata) 

 seems to be identical with orbicularis, as Mr. Agassiz himself suggests is probable. 

 Since the publication of the Revision, PfefTer, Doderlein, and de Meijere have 

 added species to the genus. Of PfefTer's three "new" forms, pallida can 

 hardly be considered a separate variety of lesueuri, as that species varies consid- 

 erably in color; ludwigii is so near orbicularis I find no way of separating them; 

 and elegans seems to be a young example of the same species. The record of 

 ludwigii from St. Thome must certainly be due to an erroneous label, for none 

 of the family occur in the Atlantic ocean. Doderlein's two Japanese species 

 seem to be perfectly valid and the same is apparently true of de Meijere's two 

 from the East Indies. The species Mr. Agassiz and I described in 1907 as 

 Laganum strigatum was based primarily on a specimen which proves to be a 

 Peronella and I have therefore transferred that species to this genus. It will 

 thus be seen that I find it desirable to recognize eight species of Peronella. 



Key to the Species of Peronella. 



Genital pores at proximal ends of interambulacra more or less close to madreporite. 

 Anus (i. e. center of periproct) .1.5-.30 of long radius from margin. 



Petaloid area only about .40 test-length; petals narrow, open; poriferous areas 

 nearly parallel; anal plates without spines; test flat with thin margin 



(about .06 test-length) slrigala. 



Petoloid area half test-length, or more; petals variable in form but rather broad, 

 sometimes open, especially unpaired one, but usually more or less closed 

 and pointed. 

 Margin of test thick, about .12 test-length; petaloid area, about .60 test- 

 length orbicularis. 



Margin of test thin, about .07 test-length ; petaloid area about .50 test-length, lesueuri. 

 Anus .40-.50 of long radius from margin. 



Height of test rather less than .20 of length. 



Petaloid area rather less than half test-length; margin of test very thin, about 



.06 test-length; anal plates without spines; test about as wide as long, pellucida. 

 Petaloid area more than half test-length; margin of test about .09 test-length; 

 anal plates with spines. 

 Test about nine tenths as wide as long or wider; petals open; poriferous 



areas little curved rubra. 



Test about four fifths as wide as long; petals closed; poriferous areas 



curved, converging at tip minuta. 



