Sl'KCrKS OF TKK ClIKMUNO GroITP. 1 1 O 



size of the qiiadrules. In some parts of the specimen tlie prevailing (piadrule 

 appears to l)e somewhat less than 1 mm. stpiare and this is siilxlivided by one 

 or two subordinate paii-s of spictilar bands. The entire surface shows twelve 

 of the spiral ridges and the last two interspaces near the apertural extremity 

 are divided medially ])y a much fainter ridge and elevated line. 



Dimensions. Entire length of the specimen, which seems to be ap[)ro.\i- 

 mately the original length of the cup, 70 mm.; width at the base, 9 mm.; at 

 30 mm. above the base, 15 ram.; at its greatest diameter, 30 nun. 



LoeaUty. In the upper beds of the Chemung group at Wellsville, N. Y. 

 (CoUection of E. B. Hall.) 



The following species are referred to this genus provisionally. They 

 indicate a spiral mode of growth but their structure is too imperfectly known 

 to render the definite determination of their generic characters possible. 



Helicodictya (?) Concordia, sp. nov. 



Plate xxvii, Fig. 2. 



The single specimen of this fossil is subfusiform in outline, with a 

 depressed upi)er surface ; expanding from its lower, subacute extremity 

 through somewhat more than one-half its length, thence broadly contracting 

 without revealing any definite evidence of an aperture at the upper end, 

 although the margin here is entire for a portion of its extent. The surface is 

 crossed by spiral ridges at wide and enlarging intervals. These ridges are 

 three in nimiber and on the left margin of the specimen are about 10 mm. 

 apart, this interval increasing on the right margin to 15 or 18 mm. The two 

 upper intervals are each divided in the middle by a finer ridge parallel to the 

 others. There are no reticulating ridges of corresponding size. The net-work 

 is composed of fine spicular bands among which none is consjiicuously pre- 

 dominant, though the prevailing quadrule measures about 2 mm. on a side 

 and is repeatedly subdivided. The length of this specimen is 60 mm. and its 

 greatest width 35 mm. 



While this specimen presents a specific aspect rendering it distinct from 

 associated forms, there is no very good reason for regarding it as congeneric 

 with Helicodictya trypania or as a genuine spiral Dictyosponge. Upon com- 

 parison of this with the specimen figured on Plate xvii (fig, 1), the similarity 

 in the character of the reticulum in both may be a reason for inferring that 

 the spiral direction of the ridges in H. (?) Concordia may be w holly casual, as 

 the example referred to evidently represents the apei'tural portion of a 

 regularly expanding cup, whose divergent ridges are vertical. 



