420 Miscellaneous. 



There is evidently a multitude of other forms of heutation, -whU^ 

 must be associated with the preceding. They ought to form the 

 subject of a special work. It is only by this means that the appa- 

 rent exceptions can be explained ; such as the secondary nervures of 

 Oxyacantha, Galeopsis, fmA Euphrasia, vA\\c\[v do not terminate at the 

 apex, but in the notches ; the tertiary nenures of the Ranunculi ; or 

 the circumscription of the notches by the tertiary nervures in many 

 species of jicer, with other analogous phaenomena. 



The above-mentioned forms, which are undoubtedly the most com- 

 mon, may be grouped as follows : — 



Leaves are either simple, digitate or pinnate. 



Simple leaves, which are composed only of one plate, have their 

 neuration, — ^^ • 



A. Running towards the margin (Randlanfe?-) ; when the ner^^i^^ 

 run from the central rib to the margin and terminate there ; these 

 are — 



a. Simple, when no tertiary nervures arise from the secondary 



nervures. 



b. Compound, when there are tertiary nervures. 



B. Arched {Bogenlaiifer) . Each pair of secondary nervures uniting 

 to form an arch. 



C. Running towards the apex (Spitzldufer) . Two inferior second- 

 ary nervures running between the margin and the central rib to 

 attain the apex of the leaf ; — 



a. Complete, when the two nervures actually reach the apex. 

 I). Incomplete, when the two nervures do not reach the apex, 



D. Marginal (Saumlaufer) . The two lateral nervures of the base 

 running towards the apex, following the margins throughout. — 

 Bibl. Univ. de Geneve, Oct. 1852, p. 161. 



On the Occurrence of large quantities of the Shells o/Anodo 

 cygnea on the sea-coast near Sandgate. By Francis Brent, Esq. 



Sandgate, March 21, 1853. 

 ]My dear Gray, — I noticed a curious circumstance this evening : — 

 in walking by the sea-shore I perceived large quantities of the shells 

 of Anodonta cxjgnea strewn along the beach, — either washed up at the 

 top of high- water mark, or mixed with the drift weeds and rubbish. 

 Nearly every specimen was more or less imperfect ; in most instances 

 one valve only, and part of the other remained ; in many cases, how- 

 ever, there was a singular perforation of about a quarter of an inch 

 in diameter in one of the valves, and in some instances both valves 

 were perfect, but in those cases part of the muscles that open and 

 close the shells remained. The quantity was so great, that in the 

 distance of a mile I could certainly have collected a waggon-load. 

 Now as this moUusk inhabits only fresh water, how comes it that so 

 large a quantity should be found on the sea-coast? I can only 

 account for the circumstance by the supposition that they had been 

 brought there by birds, probably Royston crows, which, during the 



