Intercalary Cartilages of Chorus Frogs 
57 
P. clarki, 18 P. nigrita, 24 P. ornata, 20 P. streckeri, and 28 P. triseriata. 
Skeletons of an additional 12 specimens were examined: 2 P. nigrita, 1 
P. ornata, 5 P. streckeri, and 4 P. triseriata. Histological preparations 
from the following representative arboreal hylids were also examined: 1 
Hyla andersoni, 1 H. chrysoscelis, 1 H. cinerea, 1 H. femoralis, 4 H. 
squirella, and 2 H. versicolor. Specimens were obtained from the Amer- 
ican Museum of Natural History, Charleston Museum, Florida State 
Museum, Illinois State University, Texas Memorial Museum, and Uni- 
versity of Southeastern Louisiana, as well as from private collections of 
L. E. Brown, R. S. Funk, and G. L. Paukstis. 
From 1 to 18 digits (usually 2) per preserved specimen were 
removed and individually labeled with letters and numbers according to 
the location of the digit on the body. Slide preparation was based pri- 
marily on the techniques of Humason (1962). Digits were moved 
through a 50% to 100% ethanol dehydration series and were vacuum 
embedded in paraffin. Serial, sagittal sections (7 microns thick) were 
prepared using a rotary microtome. Slides were stained in either Dela- 
field’s hematoxylin and eosin or Mallory’s triple stain. Representative 
whole specimens and individual digits were also cleared and stained for 
bone and cartilage following the methods of Hardaway and Williams 
(1975) and Dingerkus and Uhler (1977). Photomicrographs were taken 
with a Zeiss Photomicroscope II using Kodak High Contrast Copy Film 
at an ASA film speed of 18. Comparisons of length (distance between 
articulating surfaces) and height (determined at a right angle through 
the midpoint of the length distance) were made in the center of the 
mid-sagittal section of the intercalary cartilages. 
Morphological terminology follows Paukstis (1978). 
RESULTS 
Three major types of intercalary cartilages were found in the spec- 
imens examined. The first type was found in Hyla andersoni (Fig. 1A), 
H. chrysoscelis, H. cinerea, H. femoralis, H. squirella, H. versicolor, 
and numerous other species of arboreal Hyla examined by Paukstis 
(1978). In these species the intercalary cartilage is characterized as fol- 
lows: height greater than length; distal articulating surface generally 
more concave than proximal articulating surface; apex shorter than 
base. This type of intercalary cartilage always offsets the positions of the 
terminal and subterminal phalanges so that the terminal phalanx is dis- 
placed vertically and ventrally relative to other phalanges of the digit 
(Fig. 1A). 
The second type of intercalary cartilage was found in P. brachy- 
phona, P. brimleyi, P. clarki, P. nigrita, and P. triseriata. Their interca- 
lary cartilages are nearly cuboidal (Fig. IB). The terminal phalanx is 
offset from the other phalanges by the intercalary cartilage in the same 
manner as in the arboreal hylids examined. 
The third type of intercalary cartilage is quite reduced, with the 
curvatures of articulating surfaces nearly equal and very shallow. This 
