of the Ventriculidae of the Chalk. 



359 



Fig. P. 



is seen in the accompanying 

 figure. This can, in itself, 

 give httle idea of the form or 

 nature of the recent animal. 

 I have a specimen of this 

 aspect nine inches across. 

 Anxious to ascertain the true 

 nature of this remarkable ap- 

 pearance, of which no expla- 

 nation had ever been even 

 offered, I carefully collected 

 every fragment I could find, 

 until I was led to infer a rela- 

 tion between certain flat and 

 unconnected surfaces, some- 

 times found, and these mark- 

 ings. I was fortunate at 



length in obtaining two specimens, each of very large size, and 

 which exhibited on one end the aspect of fig. P, and on the broad 

 side, and in continuous connexion with one of the lines of that 

 peculiar marking, an entire and unbroken surface of many square 

 inches in extent. It became obvious that the inference already 

 made had been correct*; that these markings were caused by 

 the transverse section of a membrane very deeply folded up. I 

 then had recourse, as in other cases, to dissection, in order to 

 ascertain the entire form and habit of the creature, which no 

 specimen developed in the ordinary way could ever show. The 

 extreme fineness of the membrane, and the great depth of the 

 brachial fold, made the task a very difficult one. Having, how- 

 ever, succeeded in several instances, I have been able to restore, 

 from specimens thus cleared out, the beautiful and extraordinary 

 form seen in figure 0, a form of animal life seldom if ever exceeded 

 in beauty and striking evidence of design and adaptationf. 

 The wall of this species is exceedingly thin and delicate, the 



* These specimens had been shown by me to several friends, and my in- 

 ference of the habit of the animal, with a model in paper of what I con- 

 ceived its form to be, explained to them long before the importation of the 

 11th livraison of Michelin's * Iconographie Zoophytologique ' (see ante, 

 p. 80). Plate 30 of that work became an interesting illustration of the pre- 

 sent species, though giving little idea of its true character, and none what- 

 ever of its habit, on neither of which points do the accompanying descrip- 

 tions aflPord any real aid. The character of the surface is there very imper- 

 fectly represented, and the magnified views are not truthful, which they 

 could hardly be since that author had no idea of the true structure of this 

 class of fossils. 



t This figure, as well as all the other woodcuts illustrative of the present 

 subject, has been executed, with great care and faithfulness, by Mr. Frederick 

 Gyde. 



