BRACHIOPODA. 
Faminy IIJ.—RHYNCHONELLIDA.* 
HATONIA, Hall, 1859. 
Dedicated to the late Professor Amos Haton. 
Examples, Atrypa peculiaris, Conrad; A.singularis, Vanuxem, 
Shell like that of Rhynchonella ; the tower half of the ventral 
valve with a broad deep sinus. Valves articulating by means 
of two teeth in the ventral valve, with corresponding sockets in 
the dorsal valve, and a median septum embraced between the 
deeply bifurcating cardinal process of the opposite one. 
Dorsal valve with four crural processes; in the ventral valve 
the dental plates are represented by elevated lamellze surround- 
ing the muscular impression, which is much stronger and differs 
in some respects from that of Rhynchonella. 
Fossil, 7 species. Upper Silurian. United States. 
CAMERELLA, Billings, 1859. 
Examples, C. Volborthi, Billings; Atrypa extans, Hall. 
Synonym, Triplesia, Hall, 1859. 
Ventral valve with a small triangular chamber beneath the 
beak, supported by a short mesial septum as in Pentamerus. 
Dorsal valve with a single mesial septum and two short lamella 
for the support of the oral appendages, as in Ahynchonella. 
Surface smooth or obscurely plicated. 
Distribution, 9 species. Lower Silurian. North America. 
EICHWALDIA, Billings, 1858. 
Dedicated to Professor Hichwald, the celebrated Russian 
palzeontologist. 
Type, H. subtrigonalis, Lower Silurian. Canada. 
Shell with the ventral valve perforated on the umbo for the 
passage of a peduncle; the place of the foramen beneath the 
beak being occupied by an imperforate concave plate; the in- 
terior of each valve divided by a medio-longitudinal ridge, that 
of the dorsal valve very prominent; hinge and teeth sockets 
wanting. 
The internal structure of the ventral valve somewhat resem- 
bles that of Pentamerus or Camorophoria. 
Distribution, 3 species. Silurian, Canada; England. 
STRICKLANDINIA, Billings, 1863. 
Dedicated to the late Professor H. E. Strickland. 
Synonyms, Stricklandia, Billings, 1859 (non Buckman); 
Ronsseleria (pars), Hall. 
* See p. 275. 
