CO CATALOGUE OP THE BLASTOIDEA. 



at a distance from the peristome, as in our figures of Pentremites Godoni and Elcea- 

 crinus Verneuili (PI. XII. fig. 17; PI. XIX. fig. 7), the transverse striation of the 

 lancet-plate and the crenulation of the food-groove would have been the very first 

 things to disappear, though they are most extensively represented in Hambach's 

 figure under the name " covering integument." Some further remarks on the argu- 

 ments advanced by Hambach in favour of his assertion will be found in the ' Annals 

 and Magazine of Natural History ' for December 1881, p. 421, and April 1885, p. 279. 



Besides the ordinary crenulated edging of the food-groove and its lateral branches, 

 other markings may be detected on the ambulacra of Blastoids which are more than 

 usually well preserved. Although partially known to Goldfuss, they seem to have 

 altogether escaped the notice both of Roemer and of most American palaeontologists, 

 and to have been first observed by Billings in Pentremites pyrif of mis 1 . He describes 

 them in terms which are admirably illustrated by our PI. I. fig. 1. "The lateral 

 branches of the food-groove do not run directly to the ambulacral pores. Each of 

 them terminates at a point between the inner extremities of two of the pores. There 

 is at this point a small pit, which appears to be the socket of an appendage quite 

 distinct from that of the pinnule. The groove does not reach the socket of the 

 pinnule, which is situated further out, between two of the pores. On the other 

 hand, a small groove runs from each pore inward, and terminates at another socket 

 about halfway between the pore and the main median groove of the ambulacrum. 

 It would thus appear that, besides the ordinary pinnules, there were two other rows 

 of appendages on each side of the median groove." 



We are not sure that the inference contained in the last sentence is altogether a 

 safe one, but we are glad to be able to confirm the general accuracy of Billings's 

 description. The pits of the outer row which terminate the lateral branches of the 

 food-groove are sometimes totally obscured, as seen in PI. I. fig. 3 ; but in other 

 specimens they are very evident (PI. I. figs. 1, 2). They were described by Goldfuss 2 

 as a series of pores on the extremities of the transverse striae of the ambulacra 

 themselves. Troost denies the existence of pores in this position 3 , and we have no 

 doubt that he is right ; but if the word " pits" be substituted for " pores " in Goldfuss's 

 description it is perfectly correct. The inner row of pits was, however, unknown to 

 him. In Pentremites pyriformis they are situated on the side plates at the proximal 

 ends of the ambulacra (PI. I. figs. 2, 3); and this is also the case in the narrow ambulacra 

 of Mesohlastus Soioerbyi, Granatocrinus ellqdicus, G. orbicularis, and PlwnoscMsma 

 nobile (PI. VIII. figs. 5, 21 ; PI. IX. fig. 16 ; PI. XL fig. 4), while the second or 

 outer row which terminate the lateral branches of the food-groove in Pentremites 

 are altogether absent. This is no doubt due to the difference in the characters of 



1 American Journ. Sci. 1870, vol. 1. p. 228 ; Ann. & Mag. Nat. Hist. 1871, vol. vii. p. 145. 



2 Petrefacta Germanise, 1820, Th. i. p. 160. 



3 Trans. Geol. Soc. Pennsylvania, 1835, vol. i. p. 226. 



