75i DR. vr. 13. caup£3:ter ox the steuctuee, physiology, axd 



Fig. 3. Skeleton of the Pentacrinoid larva represented in Fig. 1, c, showing two rudi- 

 mentary segments of tlie Stem, tlie incipient de^•elopment of the Dorsal Cirrhi, 

 the Basals, h, h, the First, Second, and Third Iladials, r\r\ r-,r^ r^,!^, and 

 the Anal, a, now being lifted up from between the First Radials. — Magnified 

 50 diameters. 



PLATE XL. 



Fig. 1. More enlarged view of a Pentacrinoid larva of Antedon rosaceus, in a stage 

 nearly corresponding with that shown in Plate XXXIX. fig. 1, D, the nearest 

 Eay having been removed so as to bring into view the Oral apparatus : — 

 cd, Centro-dorsal plate, bearing two cirrhi, cir, cir, one rudimentary, another 

 in an ad-sanced stage of development; r\r\ r^r% r^;•■', First, Second, and 

 Thu-d Eadials ; o, o, Orals, now completely separated from the Eadials by 

 tlic intervention of the membranous Perisome. — Magnified CO diameters. 



Fig. 2. Calj^s of the same specimen seen from the other side, showing the Centro-dorsal 

 plate, cd, bearing two cirrhi, cir, cir, one rudimentary, the other still retaining 

 its rudimentary form, the First, Second, and Third Eadials, r',r\ r-,'^, r',r^, 

 and the Anal, a, now lifted out from between the First Eadials by the deve- 

 lopment of the prominent Vent, v, to which it is attached. — Magnified 60 

 diameters. 



PLATE XLI. 



Fig. 1. Skeleton of Pentacrinoid at the time of the first development of the Arms, and 

 before the first appearance of the dorsal cirrhi : — b, h, Basals ; r\ r\ Fii'st 

 Eadials ; a, Anal ; ?-^, r", Second Eadials ; o, o. Orals ; ?■^ r^, Third Eadials. — 

 ]\[agnified 100 diameters. 



Fig, 2. Separated portions of the skeleton of the Calyx of a Pentacrinoid at the epoch 

 of its detachment from the stem : — b, external and internal (dorsal and ventral) 

 faces of Basals; u', external and internal faces of First Eadials; r", external 

 and internal faces of Second Eadials ; R^, external and internal faces of Third 

 Eadials ; A, Anal ; c, ventral aspect of Centio-dorsal basin. — Magnified 100 

 diameters. 



Fig. 3. Basals in process of conversion into Eosette : — a, dorsal aspect, showing partial 

 absorption of first-formed lamella ; b, another specimen turned a little to one 

 side, showing the more complete absorption of the original lamella; 

 c, d, ventral and dorsal aspects of a basal which has been nearly modelled by 

 absorption and outgrowth into the form requisite to constitute the] Eosette 

 (Plate XXXIIT. figs. 10, 11) by union with its fellows.— Magnified 100 

 diameters. 



Fig. 4. Portion of the dried Stem of a young Pentacrinoid ; showing the prominent 

 annulus in the middle of each segment. — Magnified 70 diameters. 



