from the Bournemouth Leaf-bed. 11 



frond remains ; where it is a close and compact clay, the 

 impressions of the upper and lower epidermis are preserved, 

 and owe their colour to the decomposition of the intervening 

 tissues. The veins are represented by channels which often 

 contain the remains of fibre. Their distinctness depends upon 

 the relative decomposition of the tissues. Where the vegetable 

 matter has been quickly and entirely removed, the specimens 

 present only indistinct traces of the venation ; if, on the other 

 hand, the matrix is charged with carbonaceous matter, the 

 veins are lost in the substance of the frond, and leave no 

 traces on the impressions. 



It seems probable that these beds were deposited in a shallow 

 estuary. Large masses of wood are to be found in the cliffs 

 so honeycombed by Teredo as to leave but the thinnest parti- 

 tions between the tubes. In strata deposited under estuarine 

 conditions, we cannot look for a continuous record of events, 

 because, although the accumulation of the materials may have 

 been the work of ages, yet their final arrangement may have 

 been effected in a comparatively short space of time. 



With the exception of the Teredo-borings, few traces of 

 animal life are to be found. Remains of insects from the 

 pipe-clay at Corfe have been figured in the ' Quarterly Journal 

 of the Geological Society,' in a paper by Mr. Prestwich. I 

 have lately obtained from Bournemouth a fragment of an 

 insect, which Mr. Dallas has kindly undertaken to determine 

 if possible. 



The ferns of which I have obtained sufficiently good speci- 

 mens for description are closely allied to the recent subgenus 

 Mertensia of the genus Oleichenia. 



Subgenus Meetensites (nobis). 



Stipes repeatedly dichotomous (PI. I. fig. 2), the ultimate 

 branches bearing simply forked pinnas (figs. 1 Z>, c). Veins 

 somewhat prominent, venules free. Sori near the middle 

 of the two exterior venules of each fasciculus (fig. lg). 

 Capsules sessile, deciduous, arranged round a punctiform 

 receptacle. 



Mertensites hantoniensis (nobis). PI. I. figs. 1 a-g. 



Stipes rounded ; ultimate branches with a pair of pinna? ; 



pinna? lanceolate pinnatifid ; segments linear-acute, quite 



entire. Capsules globose, longitudinally striated, eight to 



ten in number. 



This is the fern of which I have obtained the greatest num- 

 ber of specimens. The largest in my collection are from 5 to 

 6 inches in length. It is difficult to arrive at the entire length 



