114 DlCTTOSPONOID^:. 



broken transversely at this point. There is no evidence that the pedicel is 

 filled up with spicular deposits and hence the convergence of the spicules of 

 the cup forms a sort of diajihragm which permits a ready separation of the 

 parts at this place. 



Dimensions. Of two of the best preserved examples, one measures aa 

 follows : Entire length, 170 mm., of which 93 mm. appertain to the incom- 

 plete pedicel. Width of pedicel, 10 mm.; apertural width of cup, 68 mm. 

 The other specimen has a length of 160 mm., of which but 63 belong to the 

 pedicel ; the median diameter of this cup is 45 mm., and tlie apertural width 

 about 52 mm. 



Locality. In greenish sandy stales belonging to the upper part of tlie 

 Chemung group, near Lawrenceville, Tioga county, Pennsylvania. 



BOTRYODIOTYA (or TtLODICTYA), Sp. 



From the upper beds of the Chemung group at Scio, N. Y., have 

 been obtained a few fragments of a quite small species which show com- 

 pound and pendulous nodes. These doubtless represent a species either 

 of BoTBYopicTYA or Tylodictya. (Collection of E. B. Hall.) 



IIELICODICTYA, gen. nov. 



Dictyosponges with funnel-shaped or explanate skeletons, bearing 

 equidistant spiral surface ridges. 



Type, HeUcodictya trypania, sp. nov. 



Helioodictya trypania, sp. nov. 



Plate xxii, Figs. I, 2. 



The specimen upon which this species is founded shows an elongate, 

 funnel-shaped cup of small size, subcylindrical for nearly one-half its length 

 from the base, expanding more rapidly above. Of the basal portion both 

 external and internal casts are preserved, but of the upper part only one sur- 

 face is retained. The cup is characterized by a series of strong parallel, 

 nearly ecpiidistant spiral ridges, from 4 to 5 mm. apart, ^vhich ap})ear to 

 have been extended into short, erect lamellae. The continuity of these ridges 

 about the entire surface of the cup is clearly shown upon the internal cast. 



Reticulum composed of sharply defined and minute meshes, the spicular 

 bands lying parallel and perpendicular to the spiral ridges. The latter appear 

 to con-espond to the vertical ridges in Prismodictya. The texture of the 

 reticulum is extremely fine, there being scarcely any visible distinction in the 



