242 



REPORT ON THE PENNATULIDA. 



The total length of the rachis in the Glasgow speciuien is 9 inches, 

 and the flitch at different parts is as follows, commencing at the 

 upper end : — 



First 



inch- 



Second 



Third 



Fourth 



Fifth 



Sixth 



Seventh 



Eighth 



Ninth 



-first J inch 



second J ,, 



second J ,, 



second | ,, 



9 pairs of leaves ; i.e., pitch 72 

 „ is 

 „ 16 

 „ 1-1 

 „ 9 



—first 

 third 



i inch 



6 

 4 



7 

 9 



8 



n 



8 

 11 

 18 

 12 

 17 



8 



u 



8 

 11 

 18 

 24 

 68 



Lower than this the leaves could not be accurately counted without 

 putting the specimen under the microscope, which we had no oppor- 

 tunity of doing. In Fig. 1, which is drawn from the Glasgow 

 specimen, the numbers along the left-hand side of the figure indicate 

 the pitch at the points opposite which they are placed ; the number 

 48, for instance, near the top of the figure, indicating that the pitch at 

 this point IS 48 — i.e., that at this point the leaves are at the rate of 48 

 to the inch. 



In the Oban specimens the tops are wanting, but the lower ends of 

 the rachis are, in four out of the seven specimens, perfect ; and in 

 these we have ineasured the pitch at different points, in order to 

 compare with the Glasgow specimen. In one specimen which we 

 select as apparently a fairly typical one, the total length of rachis is, 

 as in the Glasgow example, nine inches ; but as the top has gone, the 

 specimen when entire must have been considerably longer. The 

 measurements of this specimen are as follows, commencing at the 

 upper (truncated) end : — ■ 



6 

 

 6 

 7 

 9 



12 

 15 

 23 

 32 

 48 



A comparison of this with the other Oban specimens has led us to 

 a few general results of some interest. In the first place, we find that 

 in no one of the specimens is the pitch at any part less than 6 ; i.e., in 

 no part are there less than six pairs of leaves in an inch length of 

 rachis. We have already seen that the largest of the leaves are those 

 which are furthest apart, so that it would appear that, so far as the 

 Oban specimens are concerned, the limits of growth of the leaves are 

 reached when theses have attained a distance from one another of J in. 



