ECHINOIDEA. I. 115 



than others, when it has first been published. I must decidedly follow Bell and de Loriol in the 

 opinion that the name of Tripneustes has the priority. 



The species <tEchinus Robillardi, darnleyensis, and verruculatus belong, as stated above, also 

 here, but to which genus? They have, all of them, a primary tubercle on all the ambulacral plates; 

 by this feature they are excluded from the genera Toxopneustes and Tripneustes, this character being 

 here evidently of rather more value than among the cAmus-species. They must 'then either be 

 referred to Psammechinus or form a new genus. In verniculatus the buccal membrane contains 

 numerous fenestrated plates, to be sure much smaller and finer than in variegatus, where the buccal 

 membrane is closely covered with large, thick plates; but in this respect semitubcrculatus keeps an 

 intermediate position between the two, so that no definite limit can be given. The feature is quite 

 analogous with that of Parcchinus microtubcrculatus, miliaris, and angulosus. Otherwise I can see no 

 character that would justify a referring of this species to another genus. The mouth-slits are in no way 

 smaller than in small specimens of variegatus of a corresponding size; in a specimen of verruculatus 

 of a diameter of 2i mm they have a depth of i mm , in a specimen of variegatus of a diameter of 23 mm 

 they have only the same depth. Further the coloration of the test in young variegatus is so very 

 similar to that typical of verruculatus, that a comparison gives the immediate impression that they 

 must be very closely allied. Accordingly I can only regard it as correct to refer this species to the 

 genus Psammechinus, where it has already been referred by L/iitken who did not, to be sure, inter- 

 pret the genus Psammechinus in the way it is done here, since he establishes the gemis Psilechinus 

 for Ps. variegatus, and in the same paragraph he names verruculatus as a typical Psammechinus*}. 



The species Robillardi and darnleyensis are distinguished from Psammechinus by their naked 

 buccal membrane; it is, as described above, quite naked with the exception of the buccal plates, but 

 contains more or fewer irregular spicules in the inner edge. The spicules of the pedicellariae are not 

 quite dumb-bell-shaped as in verruculatus and the other Psammec/tmus-species, but are formed as 

 bows, which are a little thicker at the ends or of the same thickness in their whole length. These 

 two features, I think, render the referring to the genus Psammechinus impossible, and they must con- 

 sequently form a separate genus, for which I propose the name of Gymnechinus. 



Whether Toxopn. maculatus really belongs to Toxopneustes or must rather be referred to 

 another genus cannot be decided from the existing descriptions. 



To the genus Evechinus Verr. are referred the species chloroticus (Val.), australitz Woods, and 

 rarituberculatus Bell; of these I have examined chloroticus and rarituberculatus (the type specimen), 

 with regard to which I can give the following informations in addition to what is hitherto known. 



Evechinus chloroticus (Val.). The 4 5 nethermost ambulacral plates have all a primary 

 tubercle, then only every other plate, and above the ambitus only every third plate has a primary 

 tubercle. In small specimens a primary tubercle will thus be found on every other plate on the ab- 

 actinal side. The small spines are club-shaped. The buccal membrane inside and outside the buccal 

 plates is richly provided with rather small, simple fenestrated plates, some of those outside the buccal 

 plates are complicate and carry pedicellarise. No spines on the buccal plates. The globiferous pedi- 

 cellariae (PI. XIX. Figs. 6, 12) are very characteristic. There is only one unpaired, very strong lateral 



') Bidrag til Kundskab om Echiniderne. p. 27. 



IS* 



