and allied Brachiopod genera. 397 
be found to differ from true Retzia, taking its place near Rhyn- 
chospira. 
So long as we remain unacquainted with the interior of the 
shell, we are compelled to refer the species to some genus having 
similar external forms, though the fibrous or punctate texture 
may in many instances prove a valuable aid in these references. 
Among the forms most difficult to determine, are t umer- 
ous smooth or finely striated terebratuloid shells, having either 
ovoid, elongate, sub-circular or transverse forms. Among the 
genera of one family which in recent times have been established 
and proposed to receive these, are Athyris (= Spirigera), Merista 
(= Camarium), Meristella and Charionella; while the subdivis- 
ions of the terebratuloid forms in another direction have given 
Lerebratula proper, Lerebratulina, Waldheimia, Terebratella, Cen-. 
tronella, Cryptonella, Rensseleria, etc. 
The first four are of the athyroid type, and have internal 
at as in Spirifer. The shell in all these is fibrous, and we have 
herefore in the external shell the means of separation from those of 
the other type. 
In all the latter group we find modifications of the internal ap- 
pendage, called in Zerebratula the loop; but in none of them 
Spires exist. Moreover, in ail these the external shell is punctate ; 
and we do not yet know a punctate shell, of the external char- 
acter here indicated, which contains internal spires.” 
The external characters, therefore, of the terebratuloid forms 
may be made useful jn indicating the family relations of the 
pecies, and may prevent us from referring to the family of 
Spiriferide those which belong to the family of Zerebratulide. 
In the Thirteenth Report on the State Cabinet, published in 
1860, I proposed the name of Meristella for certain forms which 
I regarded as separable from Adhyris and Merista; and for the 
Semi-plicated forms otherwise of similar character, I suggested 
_ the name Leiorhynchus. At the same time I described un- 
_ der Zerebratula the following species: 7. Lincklent, 7. rectirostra, 
_ L£ Lens and 7. planirostra ; under each one, distinctly stating the 
Shell structure to be punctate, which character at that time 
_ afforded me the principal means of distinguishing these from 
) os species of similar form, as Meristella Haskins’, M. Barrisi 
_ and 4. Doris, which, with Atrypa scitula (4th Dist. Report) = Me- 
 Tstella scitula, have at a later peroid been placed by Mr. Billings 
among the typical forms of his Genus Chariwnella. 
Having ascertained some farther characters of these punctate 
Terabratuloid shells, I proposed in the Fourteenth Heport on 
|, * The plicated forms of Retzia and Rhynchospira are of course not included in 
the designation above made. The Nucleospire also approach the terebratuloid 
(HS, but these shells have an area on the ventral valve and a different hinge 
Am. Jour. Sc1.—Szconp Serres, Vou. XXXV, No. 105.—Mar, 1863. 
si 
7 
