16 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 134 
loop of Dallina or Magellania. The cryptonelliform loop, which con- 
sists of long, slender descending branches, slender ascending elements, 
and a slender transverse band, may be the ultimate stage in the de- 
velopment of the cryptacanthiform loop and is thus a parallel develop- 
ment of the ultimate terebratellid loop. 
REFERENCES 
Croup, P: E.,, Jr. 
1942. Terebratuloid Brachiopoda of the Silurian and Devonian. Geol. Soc. 
Amer. Spec. Pap. 38, pp. i-xii, 1-182, pls. 1-26. 
Cooper, G. A. 
1956. New Pennsylvanian brachiopods. Journ. Paleont., vol. 30, No. 3, pp. 
512-530, pl. 61, fig. 1. (Issued in July.) 
Dungar, C. O., and Conpra, G. E. 
1932. Brachiopoda of the Pennsylvanian system in Nebraska. Nebraska 
Geol. Surv., Bull. 5, 2d ser., pp. 1-377, pls. 1-44. 
Ex.iott, G. F. 
1953. Brachial development and evolution in terebratelloid brachiopods. 
Biol. Rev., vol. 28, pp. 261-279. 
Wuitr, C. A., and Sr. Jonn, O. H. 
1867. Descriptions of new Subcarboniferous and Coal Measures fossils col- 
lected upon the geological survey of Iowa; together with a notice of 
new generic characters observed in two species of brachiopods. 
Trans. Chicago Acad. Sci., vol. 1, pp. 115-127. 
EXPLANATION OF PLATES 
PLATE I 
Unless otherwise stated all specimens are from Grapevine Canyon locality. 
A. Cryptacanthia prolifica Cooper, new species. 
Figs. 1-3. Dorsal, ventral, and side views, respectively, of a complete 
loop, X 6, showing the rows of spines. From a specimen in the 7 to 9 
mm. stage. Paratype U.S.N.M. No. 127205]. 
B. Glossothyropsis sp. 
Figs. 4, 5. Ventral and side views of the loop of a specimen from the 
Word formation, Glass Mountains, Tex., showing the narrow ascend- 
ing elements and the free descending branches, X 2. Figured specimen 
U.S.N.M. No. 127254. 
C. Cryptacanthia prolifica Cooper, new species. 
Fig. 6. Side view of a specimen 7.5 mm. long showing aberrant hood 
with cavity in its attachment to the descending branches, X 6. Para- 
type U.S.N.M. No. 127204n. 
D. Cryptacanthia prolifica Cooper, new species. 
Figs. 7-21. 7, View of the pedicle valve of the smallest specimen recog- 
nized as C. prolifica, X 8, paratype U.S.N.M. No. 127202j. 8-12, A 
series of 5 specimens showing juvenile forms with their open del- 
thyrium, X 4, paratypes U.S.N.M. Nos. 127205m-q, respectively. 13, 
View of the brachial valve of a complete specimen, 1, showing size ~ 
