BUFFALO SOCIETY OF NATURAL SCIENCES 221 



rypterids were widely dispersed on both continents; the later consan- 

 guinity is thus easily understood. But I think that such an assump- 

 tion is unnecessary and my reason will be readily apparent when we 

 consider the Bertie species of Dolichopterus, D. macrochirus, D. tes- 

 tudineus and D. siluriceps. The relationship of the first to a species 

 in the Shawangunk has just been discussed. Concerning the second, 

 Clarke and Ruedemann remark: "This species, as represented by the 

 single carapace, is quite similar to D. otisius. It differs from the lat- 

 ter mainly by the greater extension of the frontal portion and by the 

 more pronounced posterior contraction of the carapace. The frontal 

 transverse ridge or fold observed in the species is also seen in D. 

 otisius" (39, 275). If the two species were genetically related, this 

 more pronounced extension of the frontal portion of the carapace 

 would be predicable in the Bertie species, for according to the laws of 

 recapitulation and tachygenesis a morphological character found in 

 the adult of any species will appear at an earlier and earlier stage in 

 the ontogenetic development of its descendants, and since the appar- 

 ently orthogenetic tendency in the Shawangunk species D. otisius 

 showed a progressive modification from rounded to angular and ex- 

 tended frontal margin, the late Bertie species D. testudineus should 

 show a more protruding frontal rim than is found in the adult D. 

 otisius. The third Bertie species is D. siluriceps of which a single 

 poorly preserved carapace is known, and which cannot be compared 

 to any other species save a small form from the Shawangunk. The 

 genus Dolichopterus is not known from any other country, nor has it 

 been found in beds of later age than the Bertie. Even the three spe- 

 cies in the Bertie are so poorly represented that one wonders what 

 happened to the fauna. Of the genotype, D. macrochirus, four in- 

 complete though excellently preserved specimens are extant; of each 

 of the other two species there is a single carapace. If these euryp- 

 terids lived in the Bertie "pools" of authors, it is inconceivable that 

 not more individuals (or exoskeletons) should have been preserved; 

 if they lived in the rivers coming from Atlantica, this scarcity is ac- 

 counted for. But the study of the phylogeny of this genus leads me 

 to think that Dolichopterus was confined to the rivers of Appalachia 

 throughout its whole racial history. (Its occurrence in so fragmen- 

 tary a condition in the Bertie suggests that the few remains were 

 transported from the debouchure of some river of Appalachia and 

 carried into the Bertie muds). There is as yet too little evidence, 

 too many pages in the history are still unread, for a reasonably defi- 



