ECHINOIDEA. I. 



"5 



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

 opinion that the name of Tripiieusfcs has the priorit}-. 



The species aEchinus Robi/lardi, darnleyensis, and vcrruciilatus belong, as stated above, also 

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

 by tilis feature they are excluded from the genera Toxopneustcs and Tripnatsffs^ this character being 

 here evidentl)' of rather more value than among the -£'r///V///'.f-species. They must then either be 

 referred to PsaiiDnec/iiiiiis or form a new genus. In vcrriicnlatus the biiccal membrane contains 

 numerous fenestrated piates, to be siu'e much smaller and finer than in variegatus^ where the buccal 

 membrane is closely covered with large, thick piates; but in this respect scniihibcrcitlafus keeps an 

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

 analogous with that of Parechiniis microtitbcrcnlahis^ iiiiliaris, and angulosiis. 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 variegatiis of a correspouding size; in a specimen of verriiculatus 

 of a diameter of 21"" they have a depth of 1"^'", in a specimen of variegatus of a diameter of 23"" 

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

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

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

 genus Psaiuiiifc/niius^ where it has already been referred byLiitken — who did not, to be sure, inter- 

 pret the genus PsaiiunechiiiKs in the wa>- it is done here, since he establishes the genus Psilcclii>ius 

 for Ps. variegatus^ and in the same paragraph he names vcrrttcnlattis as a typical Psainviechimcs^). 



The species Robillardi and darnleycusis are distinguished from Psai/uiiec/iinus by their naked 

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

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

 quite dumb-bell-shaped as in vcrrucitlatus and the other Psa i/n/iechi7nt.s-s^&c{&s, 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 Psaminccliimts impossible, and the)- must con- 

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



Whether Toxopii. iiiaailatiis really belongs to Toxopiieicstcs 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.), ausfralice Woods, and 

 raritnbcrcitlatiis 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 piates have all a primary 

 tubercle, then only e\-ery other plate, and above the ambitus only ever^- 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 

 piates is richl}- provided with rather small, simple fenestrated piates, some of those outside the buccal 

 piates are complicate and carry pedicellariæ. No spines on the buccal piates. The globiferous pedi- 

 cellariæ (Pi. XIX. Figs. 6, 12) are very characteristic. There is only one unpaired, ver}- strong lateral 



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



15* 



