NO. 2 BRACHIOPOD SUPERFAMILY STENOSCISMATACEA GRANT 35 



ginning as two main vascular trunks, dividing rather symmetrically, 

 and becoming finer toward the shell margins. In the Pentameroidea, 

 on the other hand, the pallial sinuses are weakly impressed and their 

 pattern for the whole group is not known certainly. Williams (1956) 

 described the pattern of some pentameroids as lemniscate, with several 

 main trunks, in contrast to the rhynchonelloid pattern seen in the 

 Stenosci smatacea. 



The preponderance of evidence favors the currently accepted opinion 

 that the Stenoscismatacea are properly classified with the Rhynchonel- 

 loidea rather than with the Pentameroidea. However, they are suffi- 

 ciently different from most other rhynchonelloids to warrant status as 

 a separate superfamily within that suborder. 



MEASUREMENTS 



Dimensions of length, width, and thickness are included with de- 

 scriptions of all new species, and some previously described species 

 that are abundantly represented in the U.S. National Museum col- 

 lections, or are important to the phylogeny of the superfamily. These 

 measurements are presented to illustrate the range in size of species 

 and the proportions of the individual specimens. Where abundant well- 

 preserved specimens of species of the new genera Atribonium and 

 Coledium were available, the numerous measurements are summarized 

 on scatter diagrams, to show patterns of growth. 



KEY TO THE STENOSCISMATACEA 



Rhynchonelloids with spondylium and 



camarophorium Stenoscismatacea 



A. Stenoscismatacea with stolidium or uncinuliform 



outline Stenoscismatidae 



I. Rhynchonelliform Stenoscismatidae with 



stolidium, beaks smooth Stenoscismatinae 



1. Stolidium on adults of all species, costae 



commonly strong Stenoscisma 



2. Stolidium on adults of few species, costae 



commonly weak or absent Coledium* 



II. Uncinuliform Stenoscismatidae without stolidium, 



beaks costate Torynechinae 



1 . Costae fine, numerous, remnant of 



stolidium at anterior margin Torynechus 



* Small Coledium that lacks a stolidium can be distinguished from Atribonium 

 by the sharp angle of meeting of the valves of the anterior, and commonly by the 

 weak or absent costae. 



