162 MONOGRAPH OF THE FOSSIL POLYZOA OF THE 



From Membranipora and Reptoflwtrma this genus is distinguished by its special pore, 

 and from Beptqporina and the other encrusting genera, provided with special pores, it 

 can be separated by its wide aperture. 



? R. Heteropora, n. s., fig. 50. — Colony encrusting in irregular patches. Cellules in 

 a single layer, placed with but little regularity, but with a tendency to radiating 

 lines; elongate, acuminate anteriorly, broadly truncate behind. Opening sub-trian- 

 gular, with the sides convex, often approaching an oval in very long cellules. Surface 

 regularly convex, bordered anteriorly and laterally by a slightly elevated, rounded 

 edge, usually becoming obsolete as it approaches the proximal end of the cellule. 

 Special pore placed in advance of the opening, small and round. No ovarian vesicles 

 were observed. Old cellules are closed over by a continuation of the surface wall 

 totally obliterating the aperture. In this case the "special pore" is also generally 

 obliterated, merely showing a slight depression. 



From the Cretaceous, near Mullica Hill, and from Timber Creek, N. J. Rare. 



The peculiar position of the special pore in this species, would probably entitle it to 

 rank as a distinct genus from the following one, if not as the type of a new family, if 

 we follow the classification adopted by d'Orbigny, and which, as far as relates to the 

 testaceous Polyzoa, seems to be the best one yet proposed. In this classification, the 

 number and position of these openings, called by him " special pores," determine the 

 families of this suborder. The family Flustrelliclai is characterized in his synopsis as 

 being provided with " une seule pore en arriere de l'overture." There is, we conceive, 

 as wide a difference between this species and the following as exists between the 

 Escharinettida? and the Porinidce, but we prefer, for the present, to leave the matter 

 as it is, until more material shall have accumulated, when, should it be deemed ad- 

 visable to separate the two forms, we would suggest the generic name Acrotrema, 

 making the genus, necessarily, the type of a new family — Acrotremidce. 



R. tubulata, n. s., fig. 51. — Colony encrusting in a single layer. Cellules in longi- 

 tudinal and radiating lines and in pretty regular quincunx; subhexagonal to 

 subrhomboidal in form, rounded anteriorly. Opening anterior, not terminal ; sub- 

 triangular to oval ; latter form rare. Surface smooth, convex, elevated just behind 

 the mouth, from which point arises a prominent tubular pore. This tube is inclined 

 upward and forward, often overhanging the proximal edge of the mouth. 



With Membranipora sexpunctata. Locality and geological position unknown. 



The prominent special pore, placed close to the mouth, will at once characterize 

 this pretty little species. We regret that the label belonging to this specimen has 

 been misplaced. It is probably, however, from the Virginia Miocene. 



We observed no abortive cells, nor ovarian vesicles. 



