Handbook of Paleontology 363 



in genera, but an almost total change in species. Sponges 

 were a conspicuous element of the Devonian fauna and 

 particularly deserving of mention are the glass sponges 

 (Dictyospongidae) characteristic of the Upper Devonian 

 (Chemung) of certain areas. In sandstones of this age 

 in south-central New York at least five colonies of these 

 sponges have been found, comprising nearly one hundred 

 species. Corals have expanded and multiplied enor- 

 mously both in size and numbers. They are known from 

 Louisville, Kentucky, where the famous coral reef is lo- 

 cated, north into Alaska. Corals are not equally dis- 

 tributed in the different formations, but usually are com- 

 mon in the limestones and rare in the shales and sand- 

 stones since they do not thrive in muddy waters. Most 

 of the Silurian genera persist. The corals are repre- 

 sented by cup corals (Heliophyllum), honey-comb corals 

 (Favosites), organ pipe corals (Syringopora), etc. Phil- 

 lipsastraea and Acervularia are also among the reef build- 

 ers. Graptolites which were so characteristic of certain 

 Ordovician deposits and much less common in the Silu- 

 rian became almost extinct in the Devonian. A few sim- 

 ple species lived in the Lower Devonian. Cystoids are 

 rarer than in the Silurian, in fact are on the point of 

 extinction. Blastoids are locally abundant in a few 

 places, but they do not reach their culmination until the 

 Mississippian, after which they occur sparsely and dis- 

 appear with the Paleozoic. Crinoids have increased 

 greatly in numbers and variety, and contributed largely 

 to the building up of calcareous deposits. Characteristic 

 genera are Cupressocrinits, Platycrinus, Actinocrinus, 

 Dolatocrinus, Edriocrinus etc. Starfishes (Devonaster) 

 were at times also abundant and had already acquired the 



