ECHINOIDEA. I. 



99 



arranged in transverse series. The stalk of the pedicellarise consists of long calcareous threads con- 

 nected by few cross-beams. Spicnles bihamate. 



With this species must be classed Ech. melo and acutus (under which E. Flemingii, norvegicus, 

 and microstoma are to be named as synonyms, the reasons of which will be given hereafter in the 

 description of Ech. acutus]. They are distinguished from E. esculentus by having fewer and longer 

 spines, by wanting spines on the buccal plates, and by the plates in the buccal membrane being fine 

 and quite imbedded in the skin, so that it looks as if the buccal membrane were naked. Further 

 primary tubercles are also here generally wanting in more or fewer interambulacral plates besides in 

 every other ambulacral plate. The difference between melo and acutus is very slight, they seem only 

 to be differing in form and colour -- perhaps they cannot upon the whole be kept as distinct species 

 (for particulars see under the description of Ech. acutus). The pedicellarise and spicules essentially as 

 in Ech. esculentus. 



Ech. elegans. It seems almost hopeless to attempt to distinguish the species of Echinus known 

 us E. elegans, E. norvcgicus, E. melo, and E. Flemingii^, Agassiz says ( Blake Echini, p. 39), and also 

 Wyv. Thomson classes Ech. elegans among the critical species (395. p. 744). In this statement I 

 cannot at all agree with the two celebrated authors. Ech. elegans is very different from Ech. acutus; 

 the question might rather be of referring it to another genus than of confounding it with Ech. acutus. 

 The most essential difference is that it has a primary tubercle on all the ambulacral plates. The 

 globiferous pedicellarise (PL XVIII. Figs. 23) have generally two lateral teeth on either side, the tri- 

 dentate ones are somewhat shorter and broader than in the preceding species, but the edge is also 

 here set with transverse series of small teeth. In some specimens only quite small tridentate pedicel- 

 larise occur of a somewhat other form than the large ones (PI. XX. Figs. 9, 19), but in other specimens 

 both the small and the large form as well as all transitional sizes are found. Apical area, buccal 

 membrane, and spicules as in Ech. esculentus. - - The difference here stated between Ech. elegans and 

 acutus is already seen from the description of Diiben & Koren 1 ), where it is said that de primara 

 knolarne bilda paa skalet, fran anus till munnen, 20 ytterst tydliga, aldrig afbrutna rader, while it is 

 said of Ech. Flemingii (p. 267): de 10 rader primara knolar, som upptaga ambulacralplatarne, aro esom- 

 oftast afbrutna; this feature is also emphasized by the authors under Ech. norvcgicus. To be sure it 

 is not clearly seen in the Latin diagnoses, so that it is perhaps on account of the language that this 

 feature has been overlooked by the later authors 2 ) to great injury for the correctness of the determina- 

 tions; especially Ech. elegans may often have been confounded with quite red specimens of Ech. 

 norvegicus. 



Ech. Wallisi Ag. In the description of this species (Blake-Echini. p. 39) it is said that it is 



readily distinguished .... by the arrangement of the pairs of pores in sets of two. If this be correct 

 it can scarcely be an Echinus, in which genus the pores are always trigeminate; Agassiz himself, 

 however, thinks that it is closely allied to, if not identical with, Echinus Alexandria, in which the 

 pores are arranged in the common way. Agassiz further thinks it to be allied to E. Flemingii and 



J) Skandinaviens Echinodertner. p. 273. 



2 ) Thus in Bell's Catalogue of British Echinoderms it is said of Eck. aculus: each of these (the compound Ambu- 

 lacra plates) has a large primary tubercle set about the middle of each plate*, p. 146. 



13* 



