GENERA OF THE SUBORDERS ORTHOIDEA AND PENTAMEROIDEA 



deltidium. Yatsu (1902, 1905) had shown that there was no "third plate" in embryonic shells 

 and that therefore the formation of a deltidium could not have started in this way. This agam 

 raised the question: Of what significance in classification is the deltidium? In the meantime Walcott's 

 classic "Cambrian Brachiopoda" (1912) had shown that among these early forms there were no 

 Telotremata {Swantonia is not of this order, as was then believed), and that the few forms regarded 

 as Strophomenacea were probably orthoids. After we had started our studies came a penetratmg 

 little book entitled "Brachiopod Morphology and Genera (Recent and Tertiary)" by that clear- 

 thinking author, the late J. Allan Thomson, which made still more apparent the necessity for a 

 revision of the Paleozoic articulate brachiopods. 



As is well known, studies along fundamental lines take much more time than generic revision, 

 and as time wore on our Spanish castles showed signs of shrinkage, and we had to limit ourselves to 

 Paleozoic genera. Along this line we were proceeding nicely when the call came for the junior 

 author to take up a position as assistant curator in the United States National Museum, and we had 

 to write "finis" to our work with only one-half of the Protremata done and the Telotremata not 

 more than started. However, we have an abundance of results, showing that the Orthacea, or 

 rather the greater division that we are calling Orthoidea, contains the primary stock from which all 

 the articulate brachiopods have arisen! This means not only that the Pentameracea and the Stroph- 

 omenacea have evolved out of the Orthacea, but that the order Telotremata had its origin here as 

 well. We have indicated these beginnings and regret that conditions prevent our proving the 

 genetic lines. However, a need once pointed out will soon be taken up by others, though we hope 

 that it may be our privilege to follow these leads further, either through independent work by the 

 junior author, or through studies at Yale by another budding paleontologist. 



Table of the groupings discussed in the following pages 



Total New 



Orders 



Suborders (Orthoidea and Pentameroidea) 



Superfamilies 



Families 



Subfamilies 



Genera and subgenera 



Superfamilies 

 Orthacea 

 Clitambonacea 

 Dalmanellacea 

 Syntrophiacea 

 Pentameracea 



Families 

 11 (6 new) 

 2(1 " ) 

 9 (6 " ) 

 3 (2 " ) 

 3 



2 

 2 



5 



28 



20 



135 



Subfamilies 

 10 (7 new) 

 3 (2 " ) 

 5 (2 « ) 

 

 2 



2 

 2 



15 

 11 

 35 



103 



32 



Genera- 

 Subgenera 



(53 (15 new) 

 13 ( 4 " ) 

 (37 (10 " ) 



2 " ) 



4 



( 



24 ( 



) 



Old 

 2 



3 



13 

 9 



100 



Genera 

 known 

 in 1929 



!» 



I 26 



28 (15 new) 



20 (11 new) 



135 (35 new) 78 



Division of Work. — The senior author, as intimated above, made it financially possible for his 

 co-laborer to devote himself wholly for two years to this study of the Brachiopoda, and also turned 

 over to him for use his collection and library. He then sketched out the plan of work and passed 

 on the brachiopod lore accumulated during a lifetime, and stimulated by association with E. O. 

 Ulrich, James Hall, John M. Clarke, and Charles E. Beecher. The bulk of the detailed results 

 were thus attained by the junior author, under the guidance of the senior author and of our colleague. 

 Professor Carl O. Dunbar, who was at the time himself engaged in a revision of the Pennsylvanian 

 brachiopods of the Nebraska region. 



The study so carried on has led to departures from the older lore as radical as were those of 

 Hall and Clarke between the years 1 890 and 1 895. These results, we are fully aware, will in turn 

 have to face the test of new facts brought to light by later workers. Nevertheless we are content to 



