MEM. M. C. Z., IX. No. 2, —ECHINODERMATA. 11 
PASTE Tel 
Development of Crixomea (Comatula), continued. Figures from Wiiu1aM B. CARPENTER, GEORGE 
J. Attman, and Husert Lupwie. 
1-17. Comatula rosacea, continued. From William B. Carpenter, Researches on the Structure, Physiology, and 
Development of ‘Antedon (Comatula Lamk.) rosaceus, Part I., 1866. Trans. R. S. London, CLVI., 1866, 
Pls, XXXIX.-XLII. 
a, Anal plate. ed. Centrodorsal plate. 
6b. Basals. 00. Oral plates. 
br. Brachials. ri, r2, r3, First, second, and third radials. 
c. Cirri. v, Vent. 
cf. Central pore. 
1. Greatly enlarged view of a Pentacrinoid larva, in a stage nearly corresponding with that of fig. 7, the nearest 
ray haying been removed so as to bring into view the oral apparatus: cd, centrodorsal plate bearing two 
cirri, one rudimentary, the other, c, in an advanced stage of development ; 71, 72, 73, first, second, 
and third radials ; 00, orals, now completely separated from the radials by the intervention of a membra- 
nous perisome. 
2. Calyx of the same specimen, seen from the other side, showing the centrodorsal plate bearing two cirri, one 
rudimentary, the other, c, still retaining its rudimentary form ; the first, second, and third radials, 71 r!, 
7 72, 7373, and the anal plate, a, are now lifted out from between the first radials by the development 
of the prominent vent, v, to which it is attached. 
3, 4, 5, 6, 7. Pentacrinoidal larve in different stages. Figs. 4-7 are the successive stages preceding the fully 
developed Pentacrinoid stage, fig. 3. 
8. Shows the Pentaerinoid ready to assume its free condition, two rows of dorsal cirri being now completed, the 
arms being considerably elongated by the addition of new segments, and several pairs of pinnules being 
formed at their extremities. 
4. Shows the basal, }}, the circlet of first radials, 71 r1, already complete, the rudimentary second and third radi- 
als supported by this and the circlet of orals, o 0, alternating with these and resting on the first radials. 
5. Shows the incipient development of the arms from the extremities of the third radials, the relative position of 
the other parts being but little changed, and the dorsal cirri not having yet made their appearance. See 
fig. 10 for a representation of the skeleton in this stage on a larger scale. 
6. Showing the further development of the arms, the incipient opening ont of the calyx occasioned by the 
increased development of the first radials, and the first appearance of the dorsal cirri. 
. Showing the first appearance of the pinnules at the extremities of the arms, the further opening out of the 
calyx, bringing the vent to view, and the formation of the first whorl of dorsal cirri. 
8. Skeleton of an early Pentacrinoid larva, from a dried specimen, showing the mode in which the ealyx can be 
(in that stage) completely closed in by the folding together of the orals, 0 0. 
9. Skeleton of the Pentacrinoid larva of fig. 3, showing two rudimentary segments of the stem, the incipient 
development of the dorsal cirri, the basals, 54, the first, second, and third radials, and the anal, a, now 
being lifted up from between the first radials. 
10. Skeleton of Pentacrinoid at the time of the first development of the arms, and before the first appearance of 
the dorsal cirri ; 5b, basals; 71 rl, first radials ; a, anal; r? 72, second radials ; 00, orals; r?7r3, third 
= 
radials. 
11. Skeleton of the calyx of a Pentacrinoid nearly ripe for detachment, as seen from its internal or ventral aspect, 
the centrodorsal plate having been removed ; 6 4, basals ; 71 r!, first radials. 
12. The same as seen from its external or dorsal aspect; c, central pore for the passage of the sarcodie axis through 
the centrodorsal plate ; bb, basals; 7171, first radials ; 7?, second radials ; 73, third or axillary radials ; 
br, brachials; a, anal, 
