
No. 426.] CORRESPONDENCE. 507 
have us suppose that one of the plates of the ventral armor functioned 
as oral. The author’s employment of such generic and family mis- 
appellations as “ Tolypaspis " and “ Pterichthyda ” respectively, is 
contrary to all recognized principles of nomenclature. 
That part of Professor Patten’s article which embodies a redescrip- 
tion of the dorsal and ventral shields of Tremataspis, based on four 
or five unusually perfect specimens from the Isle of Oesel, possesses 
great merit, and paleontologists should be truly grateful to him for 
having increased our knowledge of this primitive chordate in several 
important respects. The more extensive memoir on the same sub- 
ject which is promised will be awaited with great interest; and 
further enlightenment with regard to the gill openings and position 
of the mouth in ostracoderms will be particularly welcome. 
C. R. EASTMAN. 
CAMBRIDGE, MASS. 
