ABSTRACTS OF PAPERS 205 



specialization than in the modern species, where only the visible leaves of the 

 fascicle are present and in limited number. In addition to these transitional 

 forms, which represent both the hard and soft pines of the present epoch, there 

 were other forms more nearly resembling our existing pines in having a defi- 

 nite limited number of fascicular leaves, namely, from two to five, but clearly 

 contrasted to living pines in the fact that they possessed rudimentary leaves 

 in the midst of the fascicular leaves. A third variant was represented by the 

 genus Prepinus, in which the leaves are not only numerous in a fascicle with 

 a leafy central growing region, but also characterized in contrast to the foliar 

 organs of all other living gymnosperms by the presence of centripetal or 

 cryptogamic wood. In this respect, as in many other, they present a striking 

 resemblance to the leaves of the Cordaitales. The bearing of these facts on 

 the conventional view that the Araucarian conifers are the oldest is discussed. 



New facts on the structure of the hypoparian trilobites were described 

 in the next paper, which was illustrated with lantern slides ; remarks by 

 Dr. Raymond. 



ORDOVIGIAN "HYPOPARIAN" GENERA OF TRILOBITES 

 BY E. O. ULRICH 



(Abstract) 



The author discussed the character, interrelations, stratigraphic position, 

 and geologic distribution of the Agnostida?, Trinucleidre, Harpedida?, and 

 Ampyxida? found in Ordovician formations in America. Most of these trilo- 

 bites were shown to have originated in the North Atlantic realm, from which 

 they invaded the Appalachian Valley troughs. Only Gryptolithus seems to 

 have had a more southern origin, most of its species having invaded the in- 

 terior continental seas by way of the Mississippi embayment. 



In general, the author definitely disapproved the prevailing view that the 

 marginal suture in the Trinucleidse and Harpediche corresponds to the facial 

 suture. He inclined instead to the opposing view, that the facial suture in 

 these trilobites ran as in the Opisthoparia and became closed by fusion early 

 in the life of individuals. He held that the marginal suture became a neces- 

 sary convenience in moulting and possible through lateral and then posterior 

 extension of the epistoma. In other words, the marginal suture represents a 

 continuance of the frontal suture of most Opisthoparia to the genal angles. 

 He pointed out also that Olenellus has a ventral plate that is comparable to 

 the ventral plate of the cephalon of Harpes. As is well known, the facial 

 suture in Olenellus is quite as thoroughly fused as in Harpes. The author 

 exhibited enlarged photographs of the latter indicating that this suture fol- 

 lowed essentially the same Opisthoparian course in both of these genera. It 

 was concluded, therefore, that the Order Hypoparia must either be abandoned 

 or preferably redefined. The author also questioned the desirability of the 

 family Endymionida?, recently proposed by Raymond, and dissents from the 

 prevailing practice of referring all Ordovician Harpedidse except Harpides to 

 Eoharpes. He prefers to return most of them to the genus Harpes. 



The Ampyxidaa were discussed at length and the genera of the family re- 



