ECHINOIDEA. II. 165 



ring below. The valves are rauch narrowed in the niiddle, the basal part being very narrow. The blade 

 is wide, deep in the middle and with sharp corners; the edge is strongly serrate almost down to the 

 articular snrface. There is a small prolongation on the ontermost of the three arches. — The tri- 

 phyllous pedicellariæ do not differ from those of lyrifcra. 



After what has been pointed out liere it is evident that the geographical and bathymetrical 

 distribution of Brissopsis lyrifera has to be considerably restricted from what was previously generally 

 accepted. The species is known with certainty only from the European Seas, from Norway to the 

 Mediterranean, from the British Seas, the Faroe Islands, South of Iceland and Denmark Strait. The 

 bath\'metrical distribution is from shallow water to ca. 200 fathoms.' It is, of course, quite possible 

 that it does really go down to considerably greater depths, like other sublittoral species of Echinoids, 

 as e. g. Echiims csculoitiis and Strongylocentrotits drobachieusis. L,ikewise it is quite possible that it 

 will prove really to occur at the American side of the Atlantic; but we cannot accept that ou the 

 previous statements; renewed investigations are needed in the light of the facts made known liere. 

 That the small specimens from the Porcupine; from 2090^ fathoms (Wyv. Thomson. Porcupine»- 

 Ech. p. 750) are not really Br. lyrifera, may be said with rather great certainty. 



The true Br. lyrifcra certainly shows considerable variation in the shape of the test, but by 

 no means so much as assumed by Agassiz, wlio has regarded the two very distinct species Br.alta 

 and atlantica (I cannot prove that Br. elongata was also confonnded with lyrifcra by Agassiz) as 

 variations only of lyrifcra.^ The «additional light> said by Agassiz to be thrown on the changes 

 we may expect to find among Spatangoids of this group in one and the same species by all the 

 very different looking specimens of '.Brissopsis lyr fer a- from the Blake was, indeed, only additional 

 confusion. In the Revision of Echini p. 356 Agassiz states of Brissopsis lyrifera that with age < the 

 lateral pairs of ambulacra gradually tend to imite, pas.sing from a strictly Brissopsis outline (PI. XIX. f. 8) 

 to Olie considered hitherto characteristic of Toxobrissus (PI. XIX. f. 9) . And further (p.355): «The cha- 

 racter of continuity of the adjoining pairs of ambulacra, wliich Desor assigns to Toxobrissus as a 

 distinguishing feature, becomes more and more apparent according to the size of the specimens; so 

 much so, that we should place Brissopsis lyrifera, when young, in Brissopsis, but when fuU grown it 

 would most decidedly pass for a Toxobrissus \ — It must be decidedly maintained that among the true 

 Brissopsis lyrifcra there is uo tendency in the posterior petals to uuite with age; they are in the fuU 

 grown specimens at least as distant as in the young ones, if not more. Even the figures given by 

 Agassiz himself in the Revision of Echini show sufficiently that the continuity of the posterior 

 petals is not a feature developed with age. PI. XIX. Pig. 9 is from a specimen 27'9'"'" long, with very 

 confluent ambulacra; but in PI. XXI. Fig. 2, representing a specimen of 49'"™, the ambulacra do not 

 show the slightest tendency to unite. Evidently the specimen figured in PL XIX. 9 is a Br. atlantica 



I In IX. Report from the Danish Biologicai Station 1899, it is recorded from 210 fathoms from the Skagerrak. 



- In the Challenger-Ech. p. 220 the greatest depth is stated to be 2435 fatlioms. 



,i In the Prelimmarj' Report on the Echini of the - .\lbatross!> (BuU. Mus. Comp. Zool. XXXII. 1898. p. 82) Agassiz 

 expresses some doubt of the correctness of referring to Brissopsis such forms as the elougate type figured in the «Blake»- 

 Ech. PI. XXVI. Fig. 7, but in the »Panamic Deep Sea Echinii> p. 191 he again speaks of «<the elongated and globular speci- 

 mens of the West Indian Brissopsis /yrifera^. 



