68 M ALONE JURASSIC FORMATION OF TEXAS. [bull. 266. 
lion, near the anterior limit of the posterior third; flanks and post- 
umbonal slopes more or less flattened; ligament external, short; sur- 
face of shell concentrically striate, or ornamented with numerous 
strong linear elevations whose development varies, and is more regu 
lar on the proximal part of the shell, while on the distal part there 
are one or two excavated zones bounded by high lines. The lines rur 
nearly straight for a considerable part of their course parallel to the 
base, turning upward more shortly at the posterior than at the ante- 
rior end of it. 
Measurements. — Height, 13 mm.; Length (restored), about 18mm. 
breadth, 10 mm. 
Occurrt znce. — A mile and a half east of Malone station. Only 3 
specimen of the typical form was obtained. Of 3 others believed t( 
be only young and compressed examples of the species, 2 are mow 
or less complete right valves, 1 of which shows a ligamental groov< 
and a strongly denticulated inner margin; and the third is a shel 
quite flattened out. All three of these young examples agree wit] 
the proximal and differ from the distal part of the type shell in hav 
ing a tendency to a rather uniform and close development of the connj 
centric linear costellre. 
The specific name refers to some resemblance which the shell pr< 
scnts in form to that of Isodonta, as represented by the type of tha 
genus, /. deshayesii Buv. 
Ajstarte? craticula sp. n. 
PI. XI. fig. 7. 
Shell small, rather ventricose, subovate, strongly depressed alon* 
a narrow zone near the posterior cardinal border from the beaks t :| 
the posterior extremity; beaks well inflated, moderately elevate* I 
placed somewhat in advance of the middle and back of the anteric i 
third: postero-dorsal flattened area separated from the rest of til 
shell by a radial angulation and itself divided into two eoneaMJ 
zones by a radial cariniform angulation; the general surface of tie 
valves ornamented rather closely with regular, blunt-topped, conce) j 
trie costelhe. which are in strong relief and separated by interval 
of about their own width. The ornamentation of this shell recal J 
the genus Trigonia. 
Measurements. — Estimated measurements only can be given, tl 
margins of both valves of the type being imperfect. The apparel 
approximate dimensions are: Height, H mm.; length, w 28 mir I 
breadth, 17 mm. 
Occurrence. — The only specimen obtained is from the locality 
miles east of Malone station. 
