354 
USES OF LOBES IN AMMONITES. 
The uses ascribed by Von Buch to the lobes 
of Ammonites in affording attachment to the 
base of the mantle around the margin of the 
transverse plates, would in no way interfere with 
the service we have assigned to the same lobes, 
in supporting the external shell against the pres- 
sure of deep water. The union of two beneficial 
results from one and the same mechanical expe- 
dient, confirms our opinion of the excellence of 
the workmanship, and increases our admiration 
of the Wisdom in which it was contrived. 
upon which the mantle of the animal rested, at the bottom of 
the outer chamber ; these saddles are distinguished in the same 
manner as the lobes — that between the dorsal and superior 
lateral lobe, forming the dorsal saddle (S. d.), that between the 
superior and inferior lateral lobes, forming the lateral saddle 
(S. L.), and that between the inferior lateral and ventral lobe, 
the ventral saddle (S. V.), This general disposition, variously 
modified, perv'ades all forms of Ammonites; but when, as in 
PI. 39, the turn of the shell increases rapidly in width, so tliat 
the last whorl nearly, or entirely, covers the preceding whorls, 
the additional part is furnished with small auxiliary lobes, vary- 
ing with the growth of the Ammonite to the number of three, 
four, or five pairs. (PI. 39, a. 1, a. 2, a. 3, a. 4, a. 5.) 
All the lobes, as they dip inwards, are subdivided by nume- 
rous dentations, which afford points of attachment to the mantle 
of the animal ; thus each lobe is flanked by a series of accessory 
lobes, and these again are provided with further symmetrical 
dentations, the extremities of which produce all the beautiful 
ajipearances of complicated foliage, which prevail through the 
family of Ammonites, and of which we have a striking example 
on the surface of PI. 38. 
The extremities of the dentations are always sharp and 
pointed, inwards, towards the air chamber, (PI. 38, d. 1.); but 
