H0L0THURIID;E, ECHINIDiE. 
441 
Thyone (Stolns) rosacea,, id. ibid. p. 122. (According to Semper, Tlolothuria 
maxima, Yo\:&\i.,=scahra, Jiig. ; Urodcjnas ehrcnbergi and gracilis, Selenlta, 
belong to Phyllophorns, Grube; Urodemas, Orcula, and IIemicrepis=Phyllo- 
phorusi) 
Tliyonclla, g. n., Verrill, Am. Joiirn. iii. p. 437. Only 10 tentacle?, of which 
the 2 inferior are smallest (in Thyonidium 20, 2 smaller alternating with 2 
larger) j the test is thicker, and filled with a large amount of calcareous 
plates. There are other differences in the oral plates, the genital organs &c. 
Type Colochirus gemmatus, Pourt. 
Thyonidium scahrum, M. Sars,=young Holothuria intcstinalis : Sars (19, 
p. 28). Oligotrochus vitrcus, Sars {1. c, p. 29), Drobalc, Ijofoden 1., 60-300 
fathoms [Skngcrralf, Ann. N. IT. (4) x. p. 470] ; Stichopus natans, Sars (1. c. 
p. 30), Lofoden 1., Manger, Ilardangerfjord, 200-300 fathoms. The (hitherto 
unpublished) characters of Oligotrochus are given as follows 
Corpus crassiusculum, seu baud multo elongatum, teres, subcylindricum 
aut subfusiforme, cute tenui, glaberrima, prseter corpuscula perpauca minu- 
tissima calcarea rotiformia multiradiata singula (non acervatim accunuilata) 
sparsa, non petiolata, sed cutiimmersa, laminis calcareis destitutum. Discus 
oralis paulo inclinatus. Tentacula 12, in partem eorum basalcm quasi in 
vaginam retractilia, non autem in corpus abscondenda, brevissima, elongato- 
conica, utrinque digitata. Musculi corporis longitudinales, 6 gracillimi, duo 
dorsales magis approximati quam ceteri fere sequidistantes. Intestinum 
ansam duplicem componens. Os anticum subventrale ; anus posticus circu- 
laris baud lobatus. Vesica poliana unica ; tubercula madreporiformia 1-3. 
Tubi genitales ramosi breves crassi fasciculus 2 componentes. Annulus cal- 
careus pharyngeus bene evolutus, humilis, e laminis (ut videtur) 10 constans, 
intime connatis, fere oeque latis, ventralibus altioribus, dorsalibus humilioribus, 
margine anteriore cuspidibus 12 triangularibus ornato. 
Ko WALEWSK Y (12), in his observations on the evolution of some MeditoiTanoan 
Ilolothuriidce, points out that a metamorphosis is only Imown in Synaptce, and 
that the Ilolothurians with terminal mouth {PendrochirotcB ?) are probably 
developed without any ; but this may possibly be otherwise in Ilolothurians 
with ventral mouth {Aspidochirotce ?), the eggs of which are smaller, pellucid, 
and without fat-globules. The author has witnessed the emission of eggs and 
spermatozoa in Psolinus brevis ” (according to the author, this species, 
hitherto very little known, and almost regarded as dubious, or as the young 
state of some Cucumaria, is abundant at Naples) and Pentacta doliolum ; the 
eggs are fecundated before emission. The embryo of the latter leaves the egg 
early, with 6 ciliated bands, 3 tentacles just beginning to appear, &c . ; that 
of the Psolinus wants the ciliated stage, and is only set free at a later stage, 
provided with 6 rather developed feelers and 2 terminal feet, water-system 
and digestive tube well developed. Sic.; those of Phyllophorus are deve- 
loped in the body-cavity. 
Echinid^. 
A. Agassiz, in his “Revision of the Echini^' reduces the recent Sea- 
urchins to 207 species, distributed into 81 genera. The following is a 
synopsis of the recognized genera, and their distribution into tribes and 
families, with the most important synonyms : — 
