S. S. Buchman — Reply to Prof. Blahe. 77 



thongli they may appear to be so. It is unfair to adversely criticize 

 genera by comparing, say, the senile metamorphoses of different 

 phylogenetic series. Such degradational forms have lost, to a 

 certain extent, the special features which distinguished the acmic 

 species of their genera. But a system which recognizes the true 

 biological relations of these homoplastic forms by placing them in 

 separate genera is far less arbitrary and far less unnatural than the 

 Waagenian system which Prof. Blake introduced to English readers,^ 

 in which homoplastic forms were arbitrarily dragged into the same 

 genus on account of similarity of outward shape, while their true 

 genealogical affinities were completely misunderstood. My efforts 

 towards a natural system of grouping founded on an interpretation 

 of Ammonite genealogy may not be correct at their first start ; but I 

 hope we may never return to so unnatural a grouping as was 

 expressed by Aegoceras, Arietites, and particularly Amaltheus. 

 " H. occidentalis has no tubercles, \_and therefore should belong to 

 another group']." Why? No new feature is introduced. There 

 are no tubercles in senile " variabilis," or in adult " jtigosa," and 

 none in " occidentalis " at any stage. It is an illustration of the law 

 of earlier inheritance. Had this loss of a feature been accompanied 

 by the appearance of some new character, I should have been inclined 

 to erect a new genus ; but in a simple case of decadence like this 

 I did not see the necessity. 



A definition by Dr. Haug is given, with which, it is said, my 

 figures do not agree, as they show no fasciculed ribs. I do not know 

 if this be a case of my descriptions " not agreeing with the author s 

 original definition " ; but this is not original — it is a quotation from 

 a letter. I have pointed out (page 154) that my figui^es do not 

 bear out these remarks ; but in Hang's original definition and figure 

 of H. occidentalis fasciculed ribs are not noted or shown. 



" H. Eseri. [^The author's figures include several species, none of 

 which agree ivith the typel" What, not figs. 3, and 4, pi. 25 with 

 Quenstedt, Ceph. pi vii. fig. 9 a-b?^ Dr. Haug wrote to me. May, 

 1890, " Vos K Eseri de la pi. 25 sont tout-a-fait typiques." 



The suture-line "fig. 6, pi. 35," is not normal, the siphonal lobe 

 being to one side. 



" G. mactra and D. Moorei " are degraded forms, and not fair 

 samples by which to test the genera. 



" G. aalense, vars. a~d [no proof given that they are the same 

 species']." I have yet to learn how it can be proved that certain 

 forms are of one species or not. 



" G. suhquadratum identical " with Saemanni, " differences assigned 

 not borne out by figures." Similar remarks are made about other 

 species in this " critical digest." I will take this as a sample. The 

 differences given are (in subquadratnm) coarser, more reflexed ribs, 

 stronger inner margin, deeper umbilicus more slowly-coiled " (page 

 202). I think that these difierences are all very noticeable in the 



^ Ceph. ; Yorkshire Lias, 1876. 



2 Allowance must be made for a slight discrepancy in the di-awing of the inner 

 margin in Quenstedt's two figures. 



