204 FUNCTIONS AND INSTINCTS. 



ones only two ; between each of these groves 

 is an alley containing nearly thirty oblique 

 double rows of orifices, eight or ten in each row. 

 These alleys terminate in a point at the upper 

 aperture of the shell and are truncated at the 

 lower. Each of the larger groves, if examined 

 internally, will be found to consist of about 

 twenty parallelograms arranged transversely and 

 united by an harmonic suture, in which the edges 

 are merely applied to each other without any 

 inequalities. These larger groves have a central 

 longitudinal ridge, at which it readily divides and 

 discovers a beautifully dentated suture, resem- 

 bling the dog's tooth of a gothic arch; 1 on the 

 side next the alleys the dentitions of the suture 

 are much less prominent and conspicuous. The 

 smaller groves have the same ridge and divide in 

 the same way, and seem to form one piece with 

 the alleys on each side of it : so that one of the 

 narrow groves with its two alleys forms the 

 support of one of the frames of the jaws. 2 These 

 narrow groves consist of about sixty transverse 

 pieces, and when divided of double that number : 

 thus wonderfully is the house in which these 

 animals reside, formed by its Divine Builder. 

 The sutures of the human skull, as anatomists 

 observe, admit of its more easy formation into a 

 spherical box : the shell of the sea-urchin is 



1 PLATE III. FIG. 3, a. 2 Ibid. FIG. 3, d. 



