E. Billings on the Genus Athyris. 51 
ther group. 4. Brachythyris McCoy, in which we find the es ena 
ally-ribbed surface of Spirifera, united with the short hinge-line of Mar. 
tinia. 5. Orthis Dal., in which there are no spiral appendages, the 
hinge-line and strie frequently spinose (as in Leptena), and the cardinal 
area common to both valves, and its sides ee toward each other at 
its angles; dorsal valve smallest.”— Op. cit., page 128. 
On page 146 of the same work, he thus concisely describes the 
genus :— 
“ Gen. Ch_—Nearly orbicular, small; no cardinal area or hinge-line; 
spiral appendages very large, filling the greater part of the shell. 
“This very interesting group possesses al] the external ‘ah astels of the 
Terebratulid#, united to the internal structure of the Spirifers, to which 
latter family it truly belongs. Professor Phillips is the only author who 
recognized the group: he forms of it his last division of the 
Spirifera, but gives no characters to ee it from Terebratula ; 
the internal structure is, however, a sure gui 
by some of the caketatiacs who are ees’ 3 Baa: 
ification advocated in this paper. Instead of Paaadig species 
With an imperforate beak such as A. tumida, the Acc mamcth of 
the word Athyris (without a door or opening), the expression, 
“in which there is no vestige of either foramen, cardinal area 
or hinge-line,” and, also, his typical figure all induce the belief 
that he had before him one or more forms with the beak entire. 
h 
not uncommon; it is figured in the Bull. de la Soc. Géol. de 
rance, with a hace beak as in Zerebratula. EL have, how- 
ever, seen numerous s Patoosdio'sp with the beak entire and im 
mida. Thiel latter species is so common that it is almost per 
eo such a collection, as he was then engaged upon, would con- 
: imens. 
tt we take the paragraph (N: o. 3) as a of the —— de- 
Scription, then A. tumida is jasiobed. on the other hand, — 
we othe ourselves to the extract from 146, it is not exclu- 
ded, as there is no reference made there to the structure of the 
oe Scars diagnosis is prea comprehensive and 
1eral in its terms to include A and Merista. 
le did not place 4. tumida in the genus, for rae at hie | 
$e 
