652 W. D. SMITH 



whole species possess it, then the term " phylogerontic " is used to 

 describe the stage. Pompeckj does not agree with Hyatt in saying 

 that this abnormal chamber may appear several times during the 

 growth of the individual, and afterward be absorbed. On the other 

 hand, he asserts that this chamber is always the.last chamber. 



In one individual only did the writer see anything that looked 

 like a resorption phenomenon, but he is of the opinion that the 

 peculiar swelling around the coil was due to some distortion of the 

 shell. Cases where the individual paused in its growth, forming 

 constrictions and building sutures close together, are quite common 

 in Scaphites, but further than these nothing pointing to an abnormal 

 chamber in the young stages similar to that found in the adult or 

 senile stages was found. 



All the normal, close-coiled, progressive ammonites, as far as the 

 writer knows, have lobes triamidian. This also is the opinion of 

 Haug, as stated above. On the other hand, Baculites, one species of 

 Lytoceras, L. alamedense, and all the species of Scaphites studied 

 show dicranidian lobes. In the matter of number of lobes it will 

 be found, on examination, that many species of Desmo^eras and 

 many ammonites of the Trias and Jura possess more lobes than are 

 found in the Scaphites. This is taken to be another sign of degeneracy. 



It seems to the writer that the reduced number of lobes and 

 saddles, and the lessening of the degree of digitation, in many of the 

 varieties of the Scaphites may be satisfactorily explained by retarda- 

 tion, i. e., failure to reach the highly developed condition of their 

 ancestors. In the fact, too, that we find simplified sutures and the 

 normal whorls together, and the presence of nodes in the young 

 stages along with other characters that are not signs of senility, we 

 have evidence of retardation. The reminiscenses of Pachydiscus 

 and Macrocephalites, also, in the young of S. nodosus quadrangularis 

 point to unequal acceleration or retardation. From Beecher's 1 

 work on spines we know that these belong to the gerontic condition, 

 and to find them appearing in the young stages at all shows the 

 working of the law of retardation. 



In Number 9, Fig. 3, is illustrated a very interesting point in this 



1 C. A. Beecher, "Origin and Significance of Spines," American Journal 0} 

 Science, Vol. VI (1898). 



