LYTECHINUS. 245 



To indicate these facts it seems desirable to use subspecific names, and the 

 characteristic Bermudian Lytechinus is accordingly designated as L. variegatus 

 atlanticus A. Ag., while that from the continental coast is called L. variegatus 

 carolinus A. Ag. 



In attempting to draw lines of division between this genus and Psammechinus 

 on the one hand and Toxopneustes on the other, there is very great difficulty 

 as the species of these genera appear to form an almost unbroken intergrading 

 series. The only sharp line appears to be in the globiferous pedicellarise, which 

 in miliaris and microtuberculatus are quite simple with lateral teeth, while in all 

 the other species, the lateral teeth are wanting and the blade is tubular with a 

 long terminal tooth which reaches its most extreme development in Toxopneustes. 

 By this character, a number of small tropical species are separated from Psam- 

 mechinus, with which genus they are otherwise quite closely allied. As however 

 they all show a more or less decided tendency to have one or two oculars insert 

 and the gill-cuts more sharply defined, it has seemed justifiable to associate 

 them with Lytechinus. The line of division between this genus and Toxop- 

 neustes is not suggested by the pedicellarise but is based on the reduction of 

 calcareous matter in the buccal membrane and the increased specialization of 

 the ambulacra in Toxopneustes. In the latter character however, the Japanese 

 species, T. elegans Dod., is very little advanced over Lytechinus, while the calcifi- 

 cation of the buccal membrane is more or less variable in both genera. 



As used here, Lytechinus is a somewhat heterogeneous group of nine species, 

 of which four are here described for the first time. Of the other five, two (varie- 

 gatus Leske from the West Indian region and semituberculatus Agas. and Des. from 

 the Panamic region) have long been known as congeneric species, while the rela- 

 tionships of the third and fourth (verruculatus Ltk. and rufus Bell from the Indo- 

 Pacific region) and the fifth (pictus Verr. from Lower California) have only 

 recently been made clear. Mortensen (1903) first pointed out the relationship 

 of verruculatus to Lytechinus and (in 1904) of rufus to verruculatus, while pictus 

 has up to the present time been confused with other species. It is therefore 

 a pleasure to now give it its rightful position as a valid species of this genus. 

 The nine species are easily distinguished from each other when adult, but young 

 specimens of the larger species are not always easily recognized, and since the 

 specific characters shown by the abactinal system and the gill-cuts are not 

 assumed fully until the individuals are 8-10 mm. in diameter or even larger, it 

 has been found necessary to base the distinctions of the following table largely 

 on color. Not having seen specimens of Bell's " Salmacis rufa" follow 



