of the Ventriculicbe of the Chalk. 363 



ropes of a tent, by which alone it is securely kept in a position 

 which, swinging on its single central support, it could not other- 

 wise sustain for an instant*. 



Such are the normal characters of this very curious and inter- 

 esting species. As was to be expected in so delicate a species, 

 specimens are, not unfrequently, found exhibiting abnormal forms; 

 owing either to displacements of the dead mass before or during 

 the process of fossilization ; or, sometimes, to incomplete deve- 

 lopment of the living mass, or accidents to the living animal, — 

 accidents to which, from its delicacy and remarkable form, it 

 would be peculiarly liable. Thus I have a flint ten inches in 

 length covered with irregular markings, but in which may I 

 think be clearly traced displaced portions of an individual of this 

 species. I have similar specimens in chalk in which it appears 

 clear that the originally flat arms have been tumbled and bent 

 over upon one another in confusion. I have myself collected 

 more than one specimen which would seem never to have had 

 more than two of the flattened arms. In such cases compensa- 

 ting provisions are found ; and, there being no large central ca- 

 vity, the lateral perforations are found larger than usual, and on 

 both edges of what thus becomes one elongated double fold. I 

 have another most interesting specimen, in which the opening of 

 the central cavity is in an abnormal position, namely on one side ; 

 but still it is there present in all its completeness, thus showing 

 the necessity and the presence of some compensation where any 

 abnormal conditions exist. There is, indeed, no species among 

 the Ventriculidse which bears more conclusive evidence to the 

 truth of the views heretofore expressed as to the character, affi- 

 nities, and habits of the recent animal than does Brachiolites an- 

 nularis. 



I cannot conclude the account of this species without express- 

 ing the strong feeling which its examination impresses of the 

 wonderful variety, and always completeness, of the contrivances 

 by which nature has effected her ever-present purpose of securing 

 the well-being and permanent safety of every creature she has 

 made. The theorists on mere-\ " Vegetative Repetition " and on 

 " Progressive Development " will find themselves equally at fault 

 in the examination of this species. There is no form which the 

 naturalist can study with greater interest, admiration and in- 

 struction than that of Brachiolites angularis. 



This species is found in both Upper and Middle Chalk. 



* The reader will recal the description of an ahnormal form of root already 

 given (p. 92). That specimen is of the genus Ventriculites. What is there 

 abnormal becomes a special character in the present species. 



t This word is used advisedly, to distinguish those who thus theorize from 

 those who philosophically inquire into the important questions of serial ho- 

 mologies. 



