Cebocephaly (hypotelorism, single-nostril nose) and ethmocephaly (hypotelorism, 
interorbital proboscis) lie in the middle of the spectrum of craniofacial 
changes associated with holoprosencephaly. Because these defects and thorough 
anatomic studies of them are rare, knowledge concerning morphologic as well as 
pathogenetic relationships is lacking. We report the autopsy findings and 
anatomic features of the dried skull of a 31 week fetus with cebocephaly and the 
craniofacial dissection of a 36 week fetus with ethmocephaly. Both manifested 
dysplastic changes of the ethmoid bone and anterior portion of the sphenoid 
bone, with concomitant hypotelorism and defects of the medial orbital walls. 
Through these latter defects, the eyes were joined in the ethmocephalic fetus 
(synophthalmia). Other changes of bone (single optic foramen, approximated 
maxillae, choanal atresia, thickened palate) and soft tissue (eccentric or fused 
extraocular muscles, single optic nerve) in both fetuses resembled those 
reported in other cases of cebocephaly and ethmocephaly, as well as cyclopia. In 
the 19th century, both cebocephaly and ethmocephaly were classified as two-orbit 
variants of cyclopia, a view supported by the present study.