388 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
tympanic bones to form the temporal bone but in some mammals the 
three remain distinct throughout life. 
In the following resume of previous work on the development of the 
squamosal in the Mammalia, no attempt has been made to obtain 
complete citation but only those articles are quoted which have been 
found to mark definite progress. 
The earliest account of the development of the temporal bone which 
I have found is the excellent one of Iverckringius (1670). He appar¬ 
ently adopts the term squamosal from some earlier writer since he 
says: “Ossis temporum binas vulgo anatomici affignant partes, 
quarum unam os petrosum, alteram squamosum appellitant.” He 
was well aware of the fact that many bones of the adult are formed by 
the fusion of distinct embryonic elements and he points out that the 
temporal bone arises by the fusion of (1) the annulus tympanicus, (2) 
the squamosum, and (3) the petrosum. He further recognizes the 
mastoid process as a part of the petrosum, in which he points out the 
existence of three ossificatory centers. He also called attention to the 
fact that the styloid process was preformed in cartilage and did not 
consider it a part of the temporal bone. 
Meckel (T5-’20, p. 112) recognized four bony elements in the human 
temporal: (1) “das Felsentheil” (pars petrosa), (2) “das Zitzentheil” 
(pars mastoidea), (3) “das Schuppentheil” (pars squamosum), and 
(4) “ der Trommelfellring” (annulus membrani tympani). But on a 
preceding page (107) of the same work he states that his “Zitzentheil” 
is only a part of the “Felsentheil.” Hence he hardly differs from 
Kerckringius in his results. 
Cuvier studied the squamosal from the comparative standpoint. 
Some of his results will be referred to later. Here it may be stated 
that, following Meckel he (’25) recognized the following elements in 
the human temporal: (1) ‘Tecailleuse et zygomatique,” (2) “la 
tympanique,” (3) “le rocher,” (4) “la partie masto'idienne.” He, 
however, regarded the mastoid as a distinct element and as will be 
pointed out later, confused our nomenclature by recognizing, among 
the membrane bones of the lower vertebrates, distinct mastoids. 
Hallmann’s well known work (’37) on the temporal bone was like¬ 
wise comparative, but while he added much to our knowledge of the 
non-mammalian forms he scarcely advanced beyond Meckel and 
Cuvier regarding the development. 
Huxley (’64) gave a clear summary of existing knowledge of the 
