172 PAL^ONTOLOGT OF NEW-YORK. 



in great contusion, as if they had grown abundantly in limited spaces, and that the action of 

 water had drifted them together where they now form masses like drifted seaweeds and kelps. 



Fig. 5 a. The concave side of a young specimen. 

 Fig. 5 h. The convex side of another larger individual. 

 Fig. 5 c. A larger imperfect frond, one half of which only remains. 

 Fig. 5 d. A fragment showing the condition of these fronds when drifted together. 

 Fig. 5 e. An enlargement of the ccUuliferous side, where the cells are strongly developed. 

 Fig. 5 /. Another fragment where the cells scarcely rise above the surface. 



Fig. 5 g. An enlargement of the non-celluliferous side, showing the form and arrangement of 

 the stigmata. 



Position and locality. This species occurs in the soft shale at Rochester and Lockport ; 

 more rarely it is found associated with the lower part of the limestone in broken masses en- 

 closing mud, and enveloped in the same material. instate Collection.) 



Genus SAGENELLA {mv. gen.). 



[Gr. (ta.yr,vi], verriculu?n.] 



A fragile membranous net or web-like bryozoum, incrusting other bodies ; cells arranged in 

 regular parallel or diverging series, more or less oblong quadrangular when in juxtaposition, 

 and separated from each other by a thin lamina of calcareous matter. 



Several species of Bryozoa of this character are known in different groups, usually occm-ing 

 as incrustations upon the Orthocerata. The general appearance is much like Flustra or Mem- 

 BRANiPORA, and they were doubtless among the earliest forms of that family of fossils. Nothing 

 remains of the structure, except the thin lamina constituting the lateral walls, with transverse 

 septa separating the cells. 



568. 1. SAGENELLA MEMBRANACEA (n. .^/>.). 



PL. XL E. Fig. 6 o, b. 



A thin membranaceous incrustation, consisting of elongated quadrangular cells, which arc 

 slightly narrowed toward each extremity ; cells arranged laterally in parallel series, with an 

 interstitial range intercalated at intervals ; cells in contiguous rows alternating, the distal ex- 

 tremity often concave ; length about six times the width. 



This species often covers surfaces of several inches upon the Orthocerata of this group, not 

 confining itself to a single species. The specimen figured is the larger extremity of an Ortho- 

 ceras more than two inches in diameter, and nearly all the exposed surface is covered. In some 

 instances this coral appears to line the inner side of the shell, where it probably affixed itself 

 after the death of the original occupant. In parts of these incrustations there is sometimes a 



