NO. 3 LOOP DEVELOPMENT OF CRYPTACANTHIA—COOPER 13 
ing with growth of the loop (cryptacanthiform stage). In the final 
stage of development the anterior cleft is completed and the descend- 
ing branches of the loop become freed of each other (early glosso- 
thyropsiform stage). 
THE LOOP OF CRYPTACANTHIA COMPACTA 
WHITE AND ST. JOHN 
Cryptacanthia compacta is the type species of the genus and for 
many years was the only known species. It is important therefore 
that the loop of the type species be clearly understood. As presently 
described and figured (Dunbar and Condra, 1932, pp. 307-309) the 
loop is depicted as a sort of cryptonelliform loop with long descending 
lamellae and long but fairly broad ascending elements. The figure 
of the loop given by Dunbar and Condra was reconstructed from 
serial sections. Study of the figured serial sections suggests that the 
ascending element is not properly restored and a new preparation of 
a loop inspired by this suspicion shows that it is entirely wrong. 
The new preparation of the loop was made on a specimen from 
Madison County, Iowa, essentially a topotype. The preparation was 
not made by the usual sectioning method although it was my inten- 
tion when I started the work to make serial sections. The first cut 
showed that the specimen was filled with clear calcite in two layers, 
an outer somewhat granular one and a solid inner layer of transparent 
light-brown calcite. On discovering this condition I scraped away the 
granular layer and part of the more solid mass beneath, washing fre- 
quently with acid to eliminate the needle marks. Soon a perfect loop 
was revealed which, however, was etched slightly too far on the dor- 
sal side. This too liberal etching removed the bulging part of the 
echmidium but left the jugum joining the descending lamellae. Study 
of the photographs makes it clear that these descending lamellae were 
joined like those from New Mexico. The preparation also reveals the 
numerous and long spines on the dorsal side of the descending lamellae 
which inspired White and St. John to name the genus Cryptacanthia. 
The specimen prepared was 5.3 mm. long and the loop measures 
exactly 4 mm. in length. On the dorsal side the descending lamellae 
are posteriorly distant but swing toward each other to be joined by 
a broad jugum 0.4 mm. long. Anteriorly from the jugum the de- 
scending lamellae are long and slender and diverge at a small angle. 
Their dorsal surface, from the posterior end of the jugum to the an- 
terior tip, is provided with long, slender, needle-like spines, the long- 
est one measuring 0.8 mm. in length. The descending lamellae an- 
terior to the jugum diverge at a low angle and curve strongly in an 
