ECHINOIDEA. 1. 99 



arranged in transverse series. The stalk of the pedicellariæ consists of long calcareons threads con- 

 nected by few cross-beams. Spicules bihamate. 



With this species must be classed Ech. mclo and acutiis (under which E. Flcii/higii\ norvegicus, 

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

 description of Ech. aciifiis). They are distinguished from E. cscnlnitus by having fewer and longer 

 spilles, by wanting spines on the buccal piates, and by the piates in the buccal niembrane being fine 

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

 primary tubercles are also liere generally wanting in more or fewer interanibulacral piates besides in 

 every other ambulacral plate. The difference between mclo and acufus 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. acutiis). The pedicellariæ and spicules esseutially as 

 in Ecli. csculenfiis. 



Ech. clcgans. It seems alniost hopeless to attempt to distinguish the species of Echinus known 

 as E. elcgans, E. norvcgiciis, E. mclo, and E. Floiiingih, Agassiz says ('■ Blake Echini. p. 39), and also 

 W }• V. T h o ni s o n classes Ech. clcgans among the critical species (395. p. 744). In this statement I 

 cannot at all agree witli the two celebrated authors. Ech. clcgans is very different from Ech. aciitus; 

 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 primar\- tubercle on all the ambulacral piates. The 

 globiferous pedicellariæ (Pi. XVIII. Fig,s. 2— 3) 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- 

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

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

 membrane, and spicules as in Ech. cscnlcnhis. — The difference here stated between Ech. clcgans and 

 acutus is aheady seen from the description of Dub en & Ko ren'), where it is said that de primåra 

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

 said of Ech. Flcmingii (p. 267): ide 10 rader primåra knolar, som upptaga ambulacralplåtarne, åro esoni- 

 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. clcgans may often have been confounded with quite red specimens of Ech, 

 norvcgicus. 



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 scarcelv 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 Alexandrii> , in which the 



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



1) Skandinaviens Echinoderuier. p. 273. 



2) Thus in Bell's »Catalogue of British Echinoderms» it is said of Ech. acutus: each of these (the compound .\uibu- 

 lacra piates) bas a large primary tubercle set about the middle of each plate->. p. 146. 



13* 



