CLASSIFICATION AND NOMENCLATURE OF SKULL PARTS 



The relations of the parts of the syncranium may be summarized according to both 

 their functions and their origins in the following scheme: 



' Olfactory region 



' Neurocranium 



Syncranium ■ 



Endocranium (deep, endosteal) 

 Dermocranium (superficial, ectosteal) 



. Branchiocranilim 



Orbital region 



Otic region 



. Basal region 



' Mandibular region (Otomandibular arch and attached 

 derm bones) 



Hyal region (Hyoid arch and attached derm bones) 



Branchial region (Branchial arches and attached derm 

 bones) 



A fuller subdivision of these parts is given below in Table I. 



TABLE I 

 A Classification of the Bones of the Typical Fish Skull (Syncranium) 



I. Neurocranium 



A Endocranial 

 (deep) 



(1) Olfactory Region 



A' Dermocranial 

 (superficial) 



Ethmoid (originally preformed in 

 cartilage) 



Rostrals and Postrostrals of ganoids, some or all of which 

 give rise to "Mesethmoid" ' ( = dermal mesethmoid) 



Nasal (possibly derived from dorsal part of antorbital of 

 palaeoniscids, bearing nasal branch of supraorbital 

 canal) 



Adnasal (? derived from ventral part of antorbital of 

 palaoniscids, bearing preorbital branch of suborbital 

 canal) 



"V'omer" ( = prevomer of tetrapods) 



ScptomaxiUa (in floor of nasal capsule) 



True Prefrontal (part of circumorbital series) sometimes 

 fused with parethmoid 



' Quotation marks used when implied homologies with tetrapod bones are incomplete, doubtful or incorrect. 



(2) Orbital Region 



Sclerotic bones 



Circumorbitals: (a) suborbitals, including: "lacrymal" (so 

 1) or preorbital, so 2 ( = "jugal"), so 3 ( = true post- 

 orbital), so 4, so 5, so 6 (dcrmosphenotic), bearing the 

 suborbital branch of the lateral-line canals; (h) supra- 

 orbitals (= pre- and postfrontals of tetrapods); (c) 

 "prefrontal" (surface) 



88 



Parethmoid (= lateral ethmoids, 

 wrongly called " prefrontals ") 



covered dorsally by 

 covered dorsolaterally by 



covered ventrolaterally by 



covered ventrally by 



covered dorsolaterally by 



