Spkcies op the CnKMUNO Group. 



139 



Their surface is smooth and usually presents such an aspect as might he 

 produced by the pressure of fine sand grains agaiirst a thin, flat b<Mly. It is 

 so extremely seldom that any traces of the spicular skeleton are retained in 

 the sandstones of the Chemung group, that the absence of such evidence here 

 is not surprising. It is possil)le that their structure is similar to that of the 

 ligulate spicules observed in I/ictysponr/ia MarcelUa. The character of the 

 apertural margin is not shown in any of the specimens. 



Hypiiant^nia seems to be a Dictyosponge in which the compacting and 

 condensation of the vertical and horizontal spicular bands has been earned to 

 an extreme, leaving between the sharply delimited bundles broad areoles 

 which in generic types like Hydnocekas, Dictyospongia, etc., would be sub- 

 divided by the minor spicular bands, or in Piiysospongia, be filled by dermalia 

 and parenchynialia. 



The only known species of Hypiiant^nia is the II. Chemvngensis, 

 Vanuxeni, and of this species but five specimens have come to our knowledge, 

 four of them being here figured. 



Hypiiant^nia Chemungensis, Vanuxem. 



Plate xxviil, Fio. 1, 2; Plate xxix, Fig. 1; Plate xlv, Pio. I, 



1842. Uflmntenia Chemungensis, Vanuxem. Geology of New York; Rept. 



Third Dist., p. 184, fig. 50. 

 1863. Uphantcenia (Jlieimingensis, Hall. Sixteenth Ann. Rept. N. Y. State 



Cab. Nat. Hist., pp. 84-87, figure (on p. 86). 

 1884. Uphant(enia OJiermmgensis, Hall. Thli-ty-fifth Ann. Rept. N. Y. State 



Mus. Nat. Hist., p. 481. 

 1890. UplMnUBTnia Chermcngensis, Lesley. Dictionary of Fossils, vol. 3, 



p. 1246. 



Sponge large, explanate, broadly saucer-shaped, or umbrella-shaped with 

 a short base of attachment. Apertural outline circular. The radiating ligu- 

 late spicular bands, all of which depart from the center or apex, ninnber 

 thirty-two in the two specimens which retain this part of the sponge ; the 

 original specimen which is approximately a quadrant of the cup indicates the 

 existence of the same number of radial bands. These, as above observed, are 

 not always equidistant, but the irregularities in this respect are not con- 

 spicuous. The concentric horizontal bands regularly increase in width 

 from apex to margin. What their number was in the completed cup it 

 is impossible to say ; the greatest radius of the largest specimen shows 



