280 Raymond — Common Devonian Urachiopods . 



sions of the cardinal angles of the young Stropheodonta are in 

 perfect condition. Unfortunately the brachial loops and spires 

 are not so well preserved, though many specimens of Eunella 

 show a large part of the loop, and in one young form it is 

 entire. Many specimens of Tropidoleptus retain the delicate 

 median septum and the crura, but the loop was uot observed. 



Perfect examples of the little ostracods of the genera Halli- 

 ella and IRrkbya, whose shells are merely a fine network, 

 were obtained, as well as many of the Phombopora-like Bryo- 

 zoa, covered with minute spinules. The pelecypods, which 

 are nearly all immature individuals, are excellently preserved, 

 and many of them retain the prodissoconch. 



The advantage of this method of collecting is shown by the 

 great number of specimens of supposedly rare species obtained. 

 Pholidops hamiltonice, which is rare in ordinary collections, is 

 extremely abundant in this material, '>nly one species being 

 more common. Pholidops oblata, of which not more than a 

 dozen specimens have been found in other localities, has here 

 been obtained by the hundreds, while Asoodietyon stellatum, 

 Atitodetus Lindstroemi, and the ostracods, which are seldom 

 found in any quantity, are very common. The whole fauna 

 consists of about 125 species, 115 of which have been thus far 

 identified, there being 10 or 12 whose specific identity is 

 uncertain, and some of these are probably new. The fauna 

 is distributed as follows : — Crustacea : Trilobita, 5 species ; 

 Ostracoda, 11 ; Cephalopoda, 1 ; Gastropoda, 8 ; Pteropoda, 3 ; 

 Pelecypoda, 16 ; Brachiopoda, 39 ; Bryozoa, 18 ; Vermes, 6 ; 

 Anthozoa, 5. 



A large proportion of the individuals of the Brachiopoda 

 are in immature stages, many of them being less than l mm in 

 length. From that size there are specimens showing all grada- 

 tions up to the adult, and, in many cases, to senile stages. 

 Series representing all these stages have been selected wher- 

 ever possible, and carefully studied, in order to ascertain what 

 changes took place in the shell during the lives of the indi- 

 viduals of the various species. 



The pioneer work of this sort was done by Beecher and 

 Clarke on material obtained from Waldron, Indiana. In the 

 memoir published by them giving the results of this work, 

 the developmental stages of 25 species, belonging to 18 

 genera, were described. Later work by Beecher, Schuchert, 

 and Cumings, has added full descriptions of several more. 

 Among the fossil brachiopods, 2 genera of the Rhyncho- 

 nellidse, 3 of the Atrypidae, 1 of the Craniidse, 1 of the 

 Eichwaldiidse, 4 of the Strophomenidse, 4 of the Orthidse, 

 and 1 of the Porambonitidse, have been studied in this way 

 up to the present time. 



