356 O. E. Beecher — Development of the Brachiopoda. 



Acanthothyris. 



Ambocoelia. 



Amphiclina. 

 *Athyris. 

 *Atretia (Cryptop 

 *Atrypa. 



Bifida. 



Bouchardia. 



Centronella. 

 *Cistella. 



Clorinda. 

 *Coelospira. 



Ccenothyris. 



Cryptonella. 



Cyrtia. 



Cyrtina. 



Dayia. 



Dictyothyris. 



Dielasma. 



Dimerella. 



Disculina. 



Eatonia. 



Eudesia. 



Eumetria. 



Glassia. 



Grunewaldtia. 

 *Hemithyris. 

 Tale Museum, New 



Hindella. 



Ismenia. 



Karpinskya. 



Kayseria. 

 ora). Kingena. 



Koninckella. 

 *Koninckina. 

 *Kraussina. 

 *Laqueus. 



Leptocoelia. 



Liorhynchus. 

 *Liothyrina. 

 *Macandrevia. 



Magas. 

 *Magellania. 

 *Martinia. 



Martinopsis. 



Megathyris. 



Megalanteris. 

 *Megerlina. 



Merista. 

 *Meristella. 

 *Meristina. 

 *Muhlfeldtia. 



Nucleospira. 



Pentagonia. 



Peregrinella. 

 Haven, Conn., March, 21, 1891. 



Platydia. 



Rensselaeria. 



Reticularia. 



Retzia. 

 *Rhynchonella. 



Rhynchonellina. 



Rhynchoporina. 



Rhynchotrema. 

 *Rhynchotreta. 

 *Spirifer. 



Spiriferina. 



Spirigerella. 



Strmgocephalus. 



Suessia. 



Syringothyris. 

 *Terebratella. 



Terebratula. 

 *Terebratuiina. 



Terebratuloidea. 



Thecospira. 



Trematospira. 



Trigonosemus. 



Uncinulus. 



Uncites. 



Zellania. 

 *Zygospira. 



EXPLANATION OF PLATE XVII. 



Atremata. 



Figure 1. — Brachial valve of Paterina labradorlca, Billings, x 3. 

 Figure 2. — Pedicle valve of young specimen, x 3. 



Primordial. Near Georgia, Vermont. 

 Figure 3. — Apex of pedicle valve of Glottidia Audebarti, Brod. x 25. 

 Figure 4. — The same; brachial valve; showing more distinctly terminal 



protegulum. x 25. Recent. Beaufort, North Carolina. 



Neotremata. 



Figure 5. — Upper valve of nepionic Orbiculoidea minuta, Hall; representing 

 protegulum (p) aud paterina stage, x 25. 



Figure 6. — More advanced condition ; showing acquisition of discinoid charac- 

 ters, x 25. 



Figure 7.— Lower valve of young specimen; showing protegulum and open 

 pedicle notch, x 25. 



Devonian, Marcellus Shale. Avon, New York. 



Figure 8.— Accelerated, discinoid, dorsal protegulum of Discinisca lozvis, Sow- 

 erby, corresponding to nealogic stage of Orbiculoidea minuta, 

 figure 6. x 25. 



