242 HAWAIIAN AND OTHER PACIFIC ECHINI. 



Ocular plates small, completely excluded from periproct (except in 

 margaritaceus) ; primary spines much longer, and primary tuber- 

 cles much larger, than secondaries; buccal membrane with more 

 or less numerous plates; valves of globiferous pedicellariae with 

 small lateral teeth on each side near tip (except in armatus); 

 spines unicolor or becoming lighter at tip; size usually large, 



often exceeding 75 mm. h. d ♦ . . . . Echinus. 



Ocular I usually, ocular V not rarely, nearly or quite insert; a 



primary tubercle on each ambulacral plate; primary' spines 



and tubercles not especially conspicuous; buccal membrane 



thin and usually bare (except in angulosus and annulatus); 



size small rarely exceeding 40 mm. h. d. and usually under 30. 



Valves of globiferous pedicellaria; with one or more lateral teeth Parechinus. 



Valves of globiferous pedicellariae with no lateral teeth . . . Nudechinus. 



Poriferous areas very broad; pore-pairs at ambitus in three distinct 



vertical series; a primary tubercle only on every second, third, or 



fourth ambulacral plate Evechinus. 



Gill-cuts deep and sharply defined; a primary tubercle usually only on every 

 second, third, or fourth ambulacral plate; valves of globiferous pedicel- 

 lariae with no lateral teeth. 

 Poriferous area not one half as broad as interporiferous; pairs of pores in 



arcs of three Toxopneuslfs. 



Poriferous area more than half as broad as interporiferous; pairs of pores 



in three, more or less well separated vertical series TripneusUs. 



Periproct excentric at right, with oculars I and II insert Gymnechinus. 



PSAMMECHINUS. 



Agassiz and Desor, 1846. Ann. Sci. Nat., (3), VI., p. 36S. 

 Type-species, Echinus miliaris Gmelin, 1788. Linn6 Syst^ Nat., cd. 13, p. 3169. 



Mortensen's extraordinary course in selecting ''Echinus varicgatus Lam'k." ' 

 as the type of this genus and i)roposing a new generic name for tniliari^ and its 

 allies ("Ingolf" Ech., pt. I, p. 108, 114) is so contrary to all the accepted rules 

 of nomenclature, that it is necessary to discuss the matter fully here. The name 

 Psannnechinus was proposed by Agassiz and Desor in 1840 for a subgenus of 



' The argument of Lambert (1906, Mcmu. CJeol. Soc. France, XIV, p. 66, footnote 3) that the use of 

 the name varicgatus for this common and well-known species is not justifiable, would be un.issailablc 

 were it not for an error in the first premise, that "Cidaris vjricgala Leske est un nl'alit^ un Tripnoustes." 

 There ran bo little question that Klein's figure, to which Lc-^ke refers, is a Tripncustes. but it is equally 

 certain tliat llie liguros of .Scl);i and (Jualtieri to which Leske also refers are the West Indian spooies, 

 long known as Toxnptteuslcs varicgatus, and a careful reading of Leske's description shows that it is 

 the latter he is describing and not a Tripncustes; his description of the ambulacra clearly proves this. 

 Moreover Leske and all tiio earlier writers (except Klein) refer to the green and white coloration, and so 

 far as known, no one has ever found a green and white Tripneustes. It seems clear therefore that rarie- 

 gatus must be retained .a-s a specific name but should be credited to lycske 1778, instead of to I«<imarck. 

 1816. The nonienrl.it ure of the geiuis Tripneustes will not suffer, for the species to which Ix>ske"s name 

 varicgata was long aiiplied, was ilescribed by Linne, and thsinka to Lovdn's work, h.as now for more than 

 twenty years borne its Linna^an name, gratilla. 



