26 JOHN M. CLARKE 



knowledge available; more exact determinations must await better 

 preserved materials. 



AREA OF OCCURRENCE 



The area of deposition in which these Devonian hexactinellids 

 are most prolific is quite distinctly limited along the line of outcrop 

 in the region running from Cattaraugus County on the west to 

 Otsego County on the east, about 150 miles; they accompany the 

 area of most typical sandy sediment. As soon as the formation 

 begins to lose in sand in its extension westward and to the east the 

 sponges disappear. 



NUMBER AND NATURE OF COLONIES 



While scattered individuals and groups of sponges occur at 

 random through these rocks and add much to the variety of the 

 fauna, it is the great plantations or colonies that are here the subject 

 of special reference. It is probable that we know as yet but few of 

 the colonies that once existed. Some have been irreparably lost 

 and doubtless others await discovery. But we may here take note 

 of the following : 



1. The Hamlin Farm Colony, Naples, Ontario County. — This 

 lies nearest the base of the formation and is the oldest of all the 

 colonies known. It appears to have been entirely composed of the 

 species Hydnoceras tuberosum Conrad, of the tuberous or "alh- 

 gator tail" type. Some hundreds of specimens have been found 

 here. 



2. The Brown Hill Colony, near Avoca, Steuben County. — Here 

 again Hydnoceras tuberosum, the type of the genus and the first of 

 all the dictyosponges to be described, is the prevailing if not the 

 exclusive form. Wagonloads of these sponges have been taken 

 from this place. 



3. The Jenks Quarry Colony, near Bath, Steuben County. — 

 The sponges here are also of the tuberous type but belong to the 

 species H. bathense, H. & C, with an occasional representative of 

 H. botr oedema H. & C. This is the largest of all the assemblages. 

 Workmen in the quarry, 30 years ago, found a layer of sandstone 

 with a "curly grain" running through it that made it unfit for their 



