228 



however, exists between these : in that encrinite evident marks are 

 seen of its having been attached to a vertebral column ; whilst in this, 

 (the tortoise encrinite) there is no trace whatever of any mode, in 

 which such a combination could have been accomplished. 



Mr. Donovan's specimen is rendered particularly interesting by the 

 two first bones of one of its arms being still adherent to one of the 

 semicircular openings, and in such a manner as not only to show 

 that its divisions were dichotomous, but also to furnish us with some 

 slight intimation of the nature of the trochitula? of which this mem- 

 ber was formed. The articulating surface of one of these may be 

 seen to be evidently formed by a slight concavity, in the centre of 

 which is a small foramen : two ridges, with a narrow intermediate de- 

 pression, passing in a line from this foramen to the two opposite points 

 in the circumference : this articulating surface closely resembles that 

 of the fossil trochites depicted Plate XIII. Fig. 40. But even with 

 this aid, I must acknowledge that rny researches respecting the arms 

 and tentaculae of this animal have been entirely unsuccessful. 



Whilst striving to connect bodies together to form the ramifying 

 arms of this animal, I however discovered two other species of en- 

 crinites, possessing similar articulating surfaces with those of the ossi- 

 culae of the .arms of the tortoise encrinus, which I shall now proceed 

 to place before you, with some other substances, w r hich bear generic 

 marks of distinction sufficient to warrant their being considered as be- 

 longing to encrinites, although not always sufficient to admit of their 

 being respectively connected, so as to make out their respective species. 



Following the particular character of the articulating surface of the 

 trochitula3 attached to the body of the tortoise encrinite, I first call 

 your attention to a fossil body, frequently found in the Kentish chalk- 

 pits,, which is of a cylindrical shape, and has at its ends two articu- 

 lating surfaces, much resembling that which is observable on the ossi- 

 culae attached to the tortoise encrinite. One of these bodies is repre- 

 sented on its matrix, Plate XIII. Fig. 35. Its surface is smooth, and 



