of the Ventriculidae of the Chalk. 309 



7. Brachiolites protensus. PI. XVI. fig. 5. 

 Membrane having a slight and irregular primary fold : brachial 

 fold in large sinuous tubular masses frequently anastomosing 

 and opening into each other, and with occasional, but irre- 

 gular, large interstices : mass very irregular and usually spread- 

 ing horizontally. 



This species will perhaps be best understood if the inquirer 

 conceives a number of the arms of B. digitatus to be more or 

 less contorted instead of straight, and to anastomose and open 

 into each other instead of always being distinct from each other 

 at all other points than their bases. The tubular folds of B.pro- 

 tensus project from the mass not very prominently, but still con- 

 spicuously and in every direction. The primary fold differs how- 

 ever, as will be seen both by the description and figure, most 

 essentially from that of B. digitatus. 



The habit of the mass is the very reverse of being compact like 

 B. labrosus ; it may best be described as sprawling, whence the 

 name; its tendency being usually to horizontal rather than 

 perpendicular extension : it does not seem to have any inclina- 

 tion to assume the globose or any other definite general figure. 

 The mouths of the tubes tend to expand as in B. labrosus, while 

 in B. digitatus their tendency, where not simply straight, is rather 

 to contract as in B. tubulatus. 



This species is from the Lower Chalk and Chalk Marl. 



I have thus laid before the reader the result of an investiga- 

 tion which has engaged most of the leisure hours of same years. 

 I am too conscious of the disadvantages under which I labour, 

 and the want of qualifications which I possess, to anticipate 

 otherwise than much criticism as to the result of that investiga- 

 tion and the execution of my task. I would only request the 

 reader to remember that the field was an entirely untrodden one - 

 and the task a new one, — "a task of no little difficulty in the ac- 

 complishment, and one that may fairly entitle him who enters 

 upon it to expect to meet with indulgence*." 



I have endeavoured to show the existence, in one, at least, of 

 the great geological epochs, of a widely extended class of animals 

 whose nature, — if the existence of a few of the forms was vaguely 

 known before, — was totally unknown, as also was their structure 

 and all that constitutes the knowledge of an organic being. I 

 have exhibited a structure as remarkable as it is novel. I have 

 shown the extraordinary variety of forms which that structure 

 assumes, — a variety in which one Law of Unity, however, still 



* Farre, ut ante, p. H87. 

 Ann. $ Mag. N. Hist. Ser. 2. Vol. I 25 



