354 C. K Beecher — Development of the JBrachiopoda. 



Atremata. 

 (a, priv., and rprjpia, perforation.) 



Plate xvii, figures 1-4. 



Protegulum semicircular or semielliptical ; hinge line straight 

 or slightly arcuate. Growth taking place mainly around the 

 anterior and lateral margins, never enclosing or surrounding 

 the pedicle, which in all stages emerges freely between the two 

 valves, the opening being more or less shared by both. Yalves 

 inarticulate. 



Including the genera : 



Dignomia. 

 Dinobolus. 

 E.lkania. 

 Glossina. 

 *Glottidia. 

 Lakhmina. 



*Leptobolus. 

 *Lingula 



Lingulasma. 

 *Lingulops. 



Monomerella. 



Obolella. 



Obolus. 

 *Paterina. 

 Paterula. 

 Rhynobolus. 

 Trimerella. 



Neotremata. 



(reos, young, and rprffj.a, perforation.) 



Plate xvii, figures 5-12. 



Protegulum as in the preceding order in primitive forms, 

 becoming more circular, and with shorter and more arcuate 

 hinge in the pedicle valve of derived types. Growth of the 

 brachial valve tending to become peripheral. In the opposite 

 valve, the pedicle more or less surrounded by progressive 

 nealogic growth posterior to the initial hinge. Pedicle fissure 

 remaining open in primitive mature forms, becoming enclosed 

 in secondary forms during nealogic stages, and in derived 

 types enclosed in early nealogic or nepionic stages. Yalves 

 inarticulate. 



Including the genera : — 



Ancistoerania. 



Acrothele. 



Acrotreta. 

 *Conotreta. 

 *Crania. 

 *Craniella. 



Craniscus. 

 *Discina. 

 *Discinisca. 



*Discinopsis. 



Helmersenia. 



Iphidea. 



Kayserlingia. 



Lindstrcemella. 

 *Linnarssonia. 



Mesotreta. 

 *(Ehlertella. 



*Orbiculoidea. 



Pseudocrania. 

 *Roemerella. 

 *Schizambon. 

 *Schizobolus. 

 *Schizocrania. 



Siphonotreta. 

 *Trematis. 



