36 ROY L. MOODIE 



and Microsauria in structure and composition. The elongation 

 of the epiotic regions to form the wide, fan-shaped, horns, the 

 fusion of the frontals and the absence of a parietal foramen are 

 individual or ordinal characters the importance of which is open 

 to debate. That the fan-shaped horns were developed for the 

 protection of gills would seem most absurd. If the creatures 

 had gills the horns probably served to protect them but there 

 is no evidence whatever that these forms were branchiate. Horns 

 of a similar character are developed in many of the Microsauria 

 in genera which are otherwise and structurally unrelated. Just 

 what the development of these horns may mean is a difficult 

 problem. The solution offered by Beecher of the significance of 

 spines and horny excrescences indicating decadence may be a 

 good one here but we know so very little about these creatures 

 that conclusions would be premature. 



When we consider the characters broadly we perceive that 

 they indicate a group separation of the species of Diplocaulus 

 as I have already indicated (Geol. Mag., May, '09, p. 220). The 

 characters which have been discussed ally the present genus with 

 the Branchiosauria rather than with the Microsauria. The only 

 character of the microsaurs which the species of Diplocaulus 

 possess is the sculptured nature of the elements of the clavicular 

 girdle and cranial elements. The characters of the ribs and ver- 

 tebrae are essentially those of the Branchiosauria but they differ 

 from these in the specialization of the zygosphene and zygantrum, 

 which have not been detected in the branchiosaurs, and in the 

 structure of the ribs. The fact that the ribs are borne on the 

 middle of the centrum on an elongate transverse process would be 

 sufhcient to indicate its complete separation from the Micro- 

 sauria in which the ribs are universally intercentral. The pres- 

 ence of an epicondylar foramen in the humerus is another distinc- 

 tive character of Diplocaulus and entirely lacking in both Bran- 

 chiosauria and Microsauria. In short the characters presented 

 by Diplocaulus are so confusing and contradictory that they compel 

 us to perceive that after all a final classification is impossible. 

 There will always be new classifications so long as there are new 

 forms and new intellects at work upon the material. But if we 



