MEM. M. C. Z., IX. No. 2. — ECHINODEEMATA. 11 



PLATE II. 



Development of CmsowEA (Comatula), continued. Figures from William B. Carpenter, George 



J. Allman, mid Hubert Ludwig. 



1-17. Comatida rosacea, continued. From William B. Carpenter, Researches on the Structure, Physiology, and 

 Development of Antedou (Comatula Lamk. ) rosaceus. Part I., 1866. Trans. K. S. London, CLVI., 1866, 

 Pis. XXXIX.-XLII. 



c d. Centrodorsal plate. 



0. Oral plates. 



r^, r^, r^. First, second, and third radials. 



V. Vent. 



1. Greatly enlarged view of a Pentacrinoid larva, in a stage nearly corresponding with that of fig. 7, the nearest 



ray having heen 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 ; r^ r-, r^, first, second, 

 and third radials ; o o, 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 tliird radials, r' )•', 

 r^ }-2, r" c', and the anal plate, a, are now lifted out from between the first i-adials by the development 

 of the prominent vent, v, to which it is attached. 

 3, 4, 5, 6, 7. Pentacrinoidal larvae in different stages. Figs. 4-7 are the successive stages preceding the fully 

 developed Pentacrinoid stage, fig. 3. 



3. Shows the Pentacrinoid 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, h b, the circlet of first radials, r' >■', already complete, the rudimentary second and third radi- 



als supported by this and the circlet of orals, o o, 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 out of the calyx occasioned by the 



increased development of the first radials, and the first appearance of the dorsal cim. 



7. 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 calyx can be 



(in that stage) completely closed in by the folding together of the orals, o o. 



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, b h, 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 ; bb, basals ; r' /■', first radials ; a, anal ; r- r-, second radials ; o o, orals; r^r*, 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 ; b b, ba.sals ; r^ )■', first radials. 



1 2. The same as seen from its external or dorsal aspect ; c, central pore for the passage of the sarcodic axis through 



the centrodorsal plate ; bb, basals ; r^ r^, first radials ; r'^, second radials ; ?■', third or a.xillary radials ; 

 br, brachials; a, anal. 



