L 907—8.] The Inca Bone: Its Homology and Nomenclature. 587 
have been similar to one that I have to describe : “ The whole of the occipital 
bone above the upper curved lines was formed by two large triangular 
Wormian bones, united by a vertical suture, continuous with the sagittal.” 
He refers to and criticises Cloquet’s statements regarding Wormian bones. 
On turning to Cloquet’s plates (. Manual d’ Anatomic descriptive du 
Corps humain) one finds (plate 7, figs. 1, 4) Wormian bones depicted in 
the right fronto-parietal suture, and a small quadrilateral one at the 
posterior end of the sagittal suture. In fig. 2 of the same plate, two 
Wormian bones are shown in a very common position — in the limb of the 
lambdoid suture. 
From these authors, who seem to identify the inca bone with Wormian 
bones, we pass to some who make a distinction more or less completely. 
Students of human anatomy are familiar with modern descriptions of a 
separate interparietal, such as are found in Quain’s Osteology and Morris’s 
Anatomy. In these descriptions the separate interparietal corresponds in 
position and extent with the “ membranous ” portion of the occipital which, 
in course of development, has remained distinct from the “ cartilaginous ” 
portion of the same bone. Bland Sutton (A Treatise on Anatomy , edited 
by H. Morris, 1893, p. 31) figures it as a large crescentic bone, concavity 
downwards, capping the occipital. He does not call it the inca bone ; but 
it corresponds with the bone to which some other writers have applied that 
name. He says : “Not infrequently the interparietal portion remains 
separate throughout life, and may be even represented by numerous detached 
ossicles or Wormian bones.” It is to be noted that Thane in Quain’s 
Anatomy discusses this subject apart altogether from his description of 
Wormian bones. 
Leidy {Human Anatomy , London, 1889, p. 137) appears to make a dis- 
tinction between a “ sutural bone,” or a pair, which replaces to a variable 
extent the summit of the occipital, and the condition of permanent separa- 
tion of the upper division of the supraoccipital of the embryo, which 
“ appears to have been a more frequent one in some of the tribes of the 
South American people.” This “ isolated portion of the supraoccipital,” he 
says, “ corresponds with the interparietal bone of some of the lower animals, 
as in the rabbit.” 
Macalister (A Textbook of Human A natomy, London, 1899, p. 245) also 
distinguishes between Wormian bones and such a bone as the true os inca. 
He says : “ Detached ossicles, known as Wormian bones, are often to be seen 
in the lambdoid suture, and more rarely in other sutures. These result from 
the presence of supernumerary ossific centres, and are not to be confounded 
with the separate bones caused by want of union of the normal centres. 
