416 PROCEEDINGS OP THE GEOLOGICAL SOCIETY. [May 14, 



the stem may have had the calcareous periderm formed around it to 

 constitute the capitulum, and the greater or less resemblance to 

 Bimeria was established. 



The prolongation of the stem upwards, and its environment by a 

 whorl of tentacular appendages which could not lead to a meta- 

 stome, present a difficulty. If the creature was a Hydroid, these 

 tentacular appendages may have been generative instead of assimi- 

 lative, and may have belonged to the gonosome and not to the 

 trophosome. 



The arrangement is so seldom seen in the fossils, and is so 

 evidently a development superadded to an original condition, that it 

 appears to me, that after the trophosome had fulfilled its duties, 

 growth occurred, and the future trophosome was carried upwards 

 with the new stem, and the old tentacles became the supports of 

 the gonosomial apparatus, or that the stem about to be thus 

 developed was always reproductive in its physiology. 



The more the specimens with long tentacles and with those 

 which have been fractured rather close to the capitulum are ex- 

 amined, the stronger must be the belief that these elongated processes 

 were stiff at their origin, but capable of much movement at their 

 distal extremities. 



The variation in the number and length of the processes is 

 remarkable. 



The distal opening, when visible, is small. * 



It will be noticed from these observations that Dr. Allman's 

 remarks are not susceptible of much qualification. The form, if it 

 is one of the Hydroida, is anomalous, principally from the orna- 

 mentation of a rigid periderm, and from the smallness of the 

 foramen in the distal end of each tentacle. It appears, however, 

 that the cellulosity of the base is doubtful, and that the method 

 of growth is not in opposition to the characteristics of recent 

 Hydroida. 



Moreover tbe anomalous nature of some of the dermal organs of 

 other forms which are found on the same geological horizon must 

 be considered, before abandoning the opinion already expressed 

 concerning the zoological position of Palceocoryne. 



Thus, there is a group there of cylindrical-shaped corals belonging 

 to the genus Heterophyllia (M'Coy). Its species are very well 

 marked ; but one 'has rows of long movable spines with ball-and- 

 socket joints arranged longitudinally on its outside surface. There 

 is nothing like this external arrangement (as seen in Heterophyllia 

 mirabilis, Duncan, Phil. Trans. 1867, plate xxxi. fig. 5) in any 

 other known Madreporarian, fossil or recent ; and if abnormalities 

 existed in one class, they may have done so in another. 



The opinion of Dr. Allman that Palceocoryne ought to be classed 

 with the Rhizopoda, entitled as it is to great respect, appears 

 difficult of application. 



Doubtless he was impressed especially with the cellulosity of the 

 base of the form ; and such rhizopodal genera as Carpentena and 

 Sauammullna (Carter) probably came within his memory. 



