﻿32 SMITHSONIAN" MISCELLANEOUS COLLECTIONS [VOL. 47 



ATACTOPORA ANGULARIS new species 

 (Plate VIII, 10-12) 



Zoarium, as is nearly always the case in this genus, parasitic upon 

 cephalopods. Surface generally smooth, the solid maculae seldom 

 elevated. Zocecia angular, 8-9 in 2 mm. Acanthopores less numer- 

 ous than in other species of the genus, these structures being usually 

 limited to the junction angles, while the number to each zocecium 

 rarely exceeds three. Maculae small but as usual composed of 

 small or aborted zocecia which are filled up with age by a secondary 

 deposit of dense, laminated tissue. 



Occurrence. — Lower Richmond, Waynesville, Ohio. 



Cat. Xo. 43,193, U. S. X. M. 



Genus Petigopora Ulrich 

 To ascertain whether or not certain or all of the species referred 

 to this genus are dwarfed mutations or possibly only young stages 

 of normally ramose or massive forms of other genera of the Hctcro- 

 trypides, has been a most difficult task. The problem, moreover, 

 still confronts us and its solution seems as difficult as ever. We 

 tried to show, for instance, that P. gregaria was merely the begin- 

 ning of a secondary layer of zooecia on branches of species of 

 Dekayia, but when it was found growing on all sorts of Bryozoa, and 

 that it always maintained a reasonably definite size, we realized that 

 some other explanation of its existence was in order. So we let it 

 stand, and with it the genus. The zocecial structure of P. asperula 

 Ulrich again is essentially the same as that of the associated 

 Dekayia appressa, but among the hundreds of specimens of these 

 species that we have collected there is none to connect them. 

 Finally, P. petechialis, or species resembling it, occurs almost 

 throughout the Mohawkian and Cincinnatian groups, generally in 

 association with other Heterotrypidce. We have, however, found 

 zoaria of Petigopora in horizons from which no other similar Heter- 

 otrypoids are known. At present we can regard such a fact only as 

 indicating that these small incrustations are species by themselves. 

 The following neat species occupies a well-marked horizon and is of 

 widespread occurrence geographically in the Ohio region. 



PETIGOPORA OFFULA new species 



( Not figured I 



The new species for which we propose this name differs from the 

 previously described species in forming small, usually subglobular 



