ANATOMY, &C.J ECHINIDJI. 
J^ch. 5 
Echinoderms. While adopting these theories generally in homologizing 
the genital plates in Sea-urchins with the five primitive “ inter-brachials ” 
of Starfishes, and the five “ basals ” in Crinoids (pentacrinoid larva of 
Antedoriy e.g.), and the “ ocular” plates in Urchins and young Starfishes (at 
a later time at the extremity of the arms) with the “ radials ” of Sea-lilies, 
he regards the lower basals in Encrinus, certain Pentacrini, Marsupites, and 
PalcBocrinidce as additional elements, which are unrepresented in the other 
Echinoderms. He further regards all the annular segments of the 
crinoidal stem in the same light, and believes that the central (sur-anal) 
plate of the apical system of other Echinoderms is represented in the 
Crinoids not by the uppermost stem-joint or centro-dorsal piece, but by 
the discoidal plate, that forms the distal plate at the extremity of the 
stem, or the basal expansion of Holopus. In Marsupites also the centro- 
basal plate is perhaps the true one, corresponding with the sur-anal of 
Salenia, &c. 
Bchinida?. 
From the microscopical characters of the spines (12) the regular Sea 
Urchins may be divided into Acanthoccelata (spines, for the most part, 
hollow, with the central cavity surrounded by a solid ring, from which 
pass off solid wedges, making up the greater part of the spine, viz., Diade- 
matidm) and Acanthodictyota (spines, for the most part, with the axis 
occupied by a calcareous reticulation), which are subdivided into Acan- 
thostraca (^Cidaridoi ViXidi Saleniidoi : the periphery bounded by a crust, 
which differs in structure from the rest of the spine) and Acanthosphenota 
(periphery bounded by a single ring, or by .several cycles of solid wedges, 
separated more or less widely by reticular tissue) ; these are again mono- 
cyclic {Arhacia, Salenia^ Temnopleurus^ Mespilia) or polycyclic (Salmacis, 
AmblypneusteSy EchinuSy StrongylocentruSy HipponoCy ToxopneusteSy Stomo • 
pneustesy Echinometray Echinostrephus). 
Dorocidaris hlakei, sp. n., Agassiz (1), p. 185, pi. iv. (a few, 2-3, fan- 
shaped Rhahdocidaris-\i^Q spines mingled with the normal ones), Mexican 
Gulf, 168-450 fath. 
Salenia pattersoniy sp. n., id. 1. c. p. 187, pi. v., Mexican Gulf, 175-242 
fath. The “ S. varispina ” figured in the “ Atlantic, ’ p. 144, is regarded 
by Duncan (4, p. 59) as probably a distinct species, suggestive in certain 
respects of Acrosalenia. Agassiz (Z. c. p. 186) maintains that the true 
S. varispina is only a Peltastes, as suggested by Duncan (Zool. Rec. xiv. 
Ech. 6). 
Conoclypus sigsbe [e] Z, sp. n., Agassiz (1), p. 190, pis. i. & ii., Mexican 
Gulf, 95-460 fath. To this species the young specimens figured in 
“ Revision of the Echini,” pi. xvi. figs. 1-3, 8-10, as “ Echinolampas 
depressa ” are now referred. 
Eupatagus (?) longispinuSy sp. n., id. 1. c. p. 191, off Havana, 242 
fath. (known from fragments only). 
Rhmobrissus micrasteroidesy sp. n.y id. 1. c. p. 192, off Havana, 176 fath. 
Schizaster {Periaster) limicola, sp. n., id. 1. c. p. 193, pi. iii., Mexican 
Gulf, 118 fath. 
Linthia rostratay sp. n., Smith (17 a). Pacific. 
