24 Ech. 
MCIIINODERMATA. 
Gregory (3) believes that the fossil Sckizaster d’urbani was viviparous. 
The author further explains supposed specific differences in specimens 
of Temnechinus excavatus , Forbes, and Echinus henslovi , Forbes, as in- 
stances of sexual dimorphism. [Cf Camerano, supra.] 
Jaekel (1) describes a completely preserved calyx covering of Extra- 
crinus fossilis , Blumenb., sp. (= Pentacrinus briareus , Miller), from Lyme 
Regis. A comparison of it with living Pentacrinids showed it to be in no 
way abnormal. In the place where the anus should be, according to 
the analogy of living forms, there was to be seen a shallow pyramid, 
consisting of broad plates, few in number and tapering rapidly 
towards the tip, which carried lateral pegs, and on their outer side 
knobs. Thus the structure of the anal tube of this Liassic Pentacrinid 
shows a transition from the Palaeozoic Poteriocrmidce to the living 
forms. Extracrinus fossilis cannot, however, be looked upon as an 
ancestral form, on account of the remarkable development of its 
radialia prima. 
The specimen also showed that the high vaulting of the calyx, 
usually supposed to be normal, results from lateral compression of the 
calyx covering. Similarly moveable calyx coverings were possessed 
by Marsupiocrinus caelatus and Periechocrinus moniliformis ; also by 
Ichthyocrinus , which shows that a close union of Ichthyoci'inus and Cro- 
talocrinus is untenable. 
Jaekel (2) describes the external form, morphological structure, the 
microscopic structure, and phylogenetic relations of the IJ olopocrinidas 
(better known as Eugeni acrinidce). The term “ patina ” is suggested for 
the dorsal cup of articulate Crinoids. The patina is formed of a single 
circle of radial plates, usually five (exceptionally four) in number, the 
“costalia prima.” The basalia are no longer present morphologically, 
but their primitive position is proved by the course of the axial canals 
(taf. xl, figs. 7 & 8) ; they are now overgrown by the radials. The term 
“ costalia ” is proposed in all cases where the radially placed pieces do not 
suddenly become brachialia. In Holopocrinidas, the lower parts of the 
arms are attached by five articular surfaces to the patina and take part 
in limiting the body cavity, but carry no pinnulse, and consist of costalia 
ii & iii, which are either united by syzygy or fused. The latter is an 
axillary piece. The radial articular facets are described in detail (with 
figs. 3 & 4 in the text). An external ligament tends to keep the arms 
unrolled, and is opposed by an internal muscle which rolls them up. 
The third costals, or the fused second and third, are shown to have been 
axillaria, and each to have supported two small arms : the text-book 
reconstructions of Eugeniacrinus are quite at fault. The simplest type 
occurs in Cyrtocrinus nutans. The stem shows variations in the number 
of columnals. The axial canal is in the middle, and is round in section. 
The root consists pf a single irregular piece, from which usually several 
stems arise. Free ending of the stem is unknown. The minute structure 
of the calcareous pieces shows irregular meshes in the centre and very 
regular ones at the periphery, agreeing exactly with the description 
