RHIZODOXTIDiE. 
345 
inwards, and bounded by a broad smooth space; the 
posterior border of the inferior expanded half is thin, and 
immediately behind and within this border in the upper 
half there extends an inwardly and backwardly directed 
plate expanding upwards. 
Presented by Dr. Lauder Lindsay , 1876. 
21222 f. Eight clavicle, inner aspect, about 0*32 in maximum 
length, shown of one-third the natural size in Plate XII. 
fig. 3. The inferior half forms a broad triangular expan¬ 
sion, laterally compressed, and the superior extremity, 
though relatively thicker and smaller, is somewhat 
expanded in the same plane; midway the bone is antero- 
posteriorly compressed, thus having a twisted appearance, 
and the inflexion of the anterior border of the expanded 
4 
areas gradually diminishes above and below from this 
point. The postero-superior inner plate noted in Xo. 47717 
forms part of the upper expansion when viewed from the 
aspect shown in the specimen now figured, and here it is 
somewhat broken and distorted by pressure. 
Purchased , 1847. 
30533. Much crushed and broken left clavicle. Purchased , 1856. 
24841. Eight infraclavicle, inner aspect, exhibiting the elongated, 
rod-like, postero-superiorly directed process from the 
middle of its upper border. The bone is shown, of one- 
third the natural size, in PI. XII. fig. 4, and is associated 
with portions of the right mandibular ramus. 
Purchased , 1850. 
35728. More imperfect example of the left infraclavicle, showing 
the characteristic external ornament of fine reticulations. 
Purchased , 1859. 
47726. Imperfect remains of infraclavicles associated with frag¬ 
ments of mandible. Purchased , 1876. 
P. 721. Three imperfect scales ; Eurdiehouse. Egerton Coll. 
P. 3323. Three imperfect scales; Burdiehouse. Enniskillen Coll. 
An imperfect dentary bone from the St. Louis Limestone (Lower 
Carboniferous) of Alton, Illinois, XI.S.A., in the Museum of 
Columbia College, Xew York, closely resembles the corresponding 
element of It. hibberti. The laniary teeth, however, seem to be 
more compressed, with sharper edges, and the specimen is thus 
