Gl sill C. WiYILLE THOMSON ON THE MODE OF 



spicules ; and the calcareous bodies iu the wall of the intestine are 

 small and distant. The perforations in the ovarial plates in the 

 female are somewhat larger than in O. papillata ; and the ripe 

 ova in the ovary appear to be considerably larger. 



The eggs, after escaping from the ovary, are passed along on 

 the surface of the test towards the mouth ; and the smaller slightly 

 spathulate primary spines which are articulated to about the first 

 three rows of tubercles round the peristome, are bent inwards 

 over the mouth, so as to form a kind of open tent in which the 

 young are developed directly from the egg without undergoing 

 any metamorphosis ; until they have attained a diameter of about 

 2-5 miJlims., they are entirely covered witb plates, and are provided 

 with spines exceeding in length the diameter of the test. Even 

 before they have attained this size and development, the more 

 mature or more active of a brood may be seen straying away 

 beyond the limits of the " nursery," and creeping with the aid 

 of their first few pairs of tentacular feet out upon the long spines 

 of their mother ; I have frequently watched them return again after 

 a short ramble into the "marsupium." 



I am not aware that a free pseudembryo, or " pluteus," has 

 been observed in any species of the restricted family Cidaridaj ; 

 but I feel very certain tliat Cidaris papillata in the northern he- 

 misphere, except possibly in the extreme north, has no marsupial 

 arrangement such as we find iu the Kerguelen Cidaris. There have 

 passed through my hands during the last few years hundreds of 

 specimens of the normal northern form, of the Mediterranean varie- 

 ties, G. lujstrioc and G. affinis {stohesii), and of the American G. 

 ahyssicola, from wide-spread localities and of all ages ; and I have 

 never found the young except singly, and never in any way spe- 

 cially associated witli breeding individuals. 



The genus Goniocidaris (Desor) seems to differ from the genus 

 Cidaris in little else tban in having a very marked, naked, zigzag, 

 vertical groove between the two rows of plates of each interambu- 

 lacral area, and one somewhat less distinct between the ranges of 

 ambulacral plates. It includes about half a dozen species, which, 

 appear to be mainly confined to the colder regions of the southern 

 hemisphere, although two of the species extend as far to the north- 

 ward as the East Indies and Natal. 



On the 28th of January, 1876, we dredged from the steam- 

 pinnace, in about 10 fathoms water, off" Cape Pembroke, at the en- 



