ulrich-bassler] revision of paleozoic bryozoa 269 



readily distinguished by the extreme tenuity of its parts, and the 

 comparative rigidity of their arrangement. The fusiform swellings 

 are not only narrower but also shorter and correspondingly farther 

 apart. R. tenuis new species of the Hamilton formation is a similarly 

 attenuate species but has longer cells. 



Only the excavations or molds of this species have been seen. 



Occurrence. — Rochester shale, Lockport, N. Y. ; Clinton lime- 

 stone, near Mifflintown, Juniata county, Pa. 



Cat. Nos. 43,116, 43,117, U. S. N. M. 



RHOPALONARIA ? ANTIQUA (Portlock) 



(Not figured) 

 1843. Entobia antiqua Portlock, Rep. on Geol. County Londonderry, 



p. 360, pi. XXI, fig. 5a. 

 1854. Cliona antiqua Morris, Cat. Brit. Foss., p. 27. 

 1866. Terebripora ? Portlocki Fisher, Nouv. Arch, de Mus. d'Hist. Nat. 



Paris, t. 12, p. 307. 



A reinvestigation of the type or typical specimens is necessary 

 before the generic position of this species can be determined without 

 question, and until this is done we prefer to refer to the species as 

 above. Although agreeing in most respects with Rhopalonaria, 

 Portlock's figure of Entobia antiqua presents a few characters that 

 cause us to make the reference doubtfully. 



Occurrence. — Silurian of Ireland. 



RHOPALONARIA ROBUSTA new species 

 (Plate LXVI, 6) 



Of this species we have seen only a single colony, but its fusiform 

 cells are so much larger and the connecting stolons so much shorter 

 than any of the other forms known that we cannot hesitate in pro- 

 nouncing it distinct. The fusiform cells average about 0.12 mm. in 

 diameter and nearly i.o mm. in length. As usual the average length 

 of those in the midrib is appreciably greater than of those forming 

 the lateral branches and their connections. 



The specimen occurs in a block of chert which contains numerous 

 natural molds of brachiopods. Originally it grew upon the inner 

 side of one of their valves. This was subsequently entirely removed 

 by solution, nothing remaining now in the mold but a siliceous 

 pseudomorph of the Rhopalonaria. R. capillaris (Dollfus) from 

 the Devonian of France is a closely allied species, but differs in 

 having elongate elliptical cells connected by proportionally much 

 longer and sharply defined stolons. 



