Ui MEMOIRS OF THE CARNEGIE MUSEUM 
thyosaurian from the Jurassic of America to have the clavicle and interclavicle 
bones preserved. The position of these elements as retained in the matrix is well 
shown in fig. 21. It will be observed that the upper extremity of the right clav- 
icle as well as the right transverse end of the interclavicle are wanting. 
Viewed anteriorly if complete the anchylosed clavicles are bow-shaped, widest at 
the middle, gradually narrowing as they turn up along the anterior borders of the 
scapule. The ends must have been directed upward, outward and backward to the 
extent that either clavicle would be opposed to the oblique roughened surface” on 
the inner anterior borders of the scapulee which look forward and upward. The 
outer or upper third must have been free from the scapula though lying parallel 
with the free end of that element. 
The left clavicle which is quite complete at its upper end is subcircular in cross- 
section. The broken end of the right clavicle is somewhat angular in cross-section. 
On the median posterior side of the blended clavicles is a deep longitudinal groove 
for the reception of the transverse portion of the interclavicle. The latter is shown 
in fig. 21 a little removed to the left from its normal place in the clavicular girdle. 
Professor H. G. Seeley has pointed out four different ways by which the clavicles 
unite in Ichthyosaurus. 1, clayvicles anchylosed or connate; 2, clavicles meeting in 
the median line; 38, clavicles not meeting but joining by squamous union with the 
extremities of the interclavicle ; 4, clavicles united by a long squamous suture. He 
adds a fifth in Ophthalmosaurus, 5, clavicles united medially by an interlacing suture. 
He considered these differences of generic value, and the fifth was one of the impor- 
tant characters upon which he based the genus Ophthalmosaurus. 
A careful comparison of Seeley’s figures and description of the clavicles of 
Ophthalmosaurus with those of specimen No. 878 shows many similarities. Although 
the presence of a suture and the interclavicle wedged in between the ends of the 
clavicles in the former seems to indicate a distinct difference from the anchylosed 
clayicles of Baptanodon which show no evidence whatever of a suture at the median 
junction. 
Interclavicle (i.cl.). — With the exception of the right end of the transverse bar 
(see fig. 21), this element appears to be complete. It is of the usual “T’’-shaped 
form, though possibly not quite so robust as observed in many members of the 
genus Ichthyosawrus. 
The inferior surface of the posterior stem is rounded transversely. The parallel 
borders of this part as they extend forward diverge rapidly forming a wide triangular 
*8Cuvier in ‘‘Ossemens Fossiles’’ as early as 1824 points out that the scapula of Ichthyosaurus has at its anterior 
edge a prominence which supports the extremity of the clavicle. 
