386 TELEOSTEI 



Group B. 



The lower members of this group preserve many primitive 

 characters, such as the median gular, mesocoracoid arch, spiral valve, 

 conus with two rows of valves, all of which are found in the first 

 sub-order only; moreover, the oviducts may have open internal 

 funnels (p. 367). There is an interorbital septum, not always 

 completely formed, however (Osteoglossidae, Galaxiidae, Gadidae). 

 With the single exception of the Gadiformes (p. 478), these fish 

 have the cranial cavity shortened, the brain situated far back, the 

 olfactory lobes lying immediately in front of the fore-brain, and the 

 elongated olfactory nerves passing forward on either side of the 

 interorbital septum when present (p. 324). There are neither 

 denticles nor Weberian ossicles. The lines of divergence among 

 the lower forms are too indistinct to be followed out with certainty. 

 The group may be divided into eight sub-orders, of which two, the 

 Esociformes and the Mugiliformes, seem to lead towards the 

 Acanthopterygii. 



Sub-Group 1. 

 Sub-Order CLUPEIFORMES (Isospondili, Malacopterygii). 



This is a purely artificial assemblage of lowly organised families 

 retaining the mesocoracoid arch, pneumatic duct, a comparatively 

 large number of vertebral segments, and numerous lepidotrichia in 

 the paired fins. The scales are cycloid as a rule. 



The segments of the lepidotrichia are not co-ossified into spines ; 

 neither is the head, as a rule, overgrown with scales, and the dermal 

 cranial bones frequently remain in their primitive position near 

 the surface (p. 213). 



It should be noticed that in the skull the parietals usually, but 

 by no means always, meet in a median suture ; the eye-muscle 

 canal is generally present ; the maxilla always, except in the 

 Albulidae, forms the posterior margin of the upper jaw ; and the 

 symplectic is absent in the Mormyridae, Phractolaemidae, and 

 Cromeriidae. The hypural bones may remain unfused (Elopidae, 

 Saurodontidae, etc.). Epineurals are generally and epipleurals 

 rarely present. A complete scapular foramen is usually developed. 

 The number of pelvic lepidotrichia varies from as many as sixteen 

 in the Elopidae to as few as five in the Osteoglossidae and 

 Stomiatidae. 



The Clupeiformes might perhaps be subdivided into two 

 groups, one containing the Elopidae, Albulidae, Osteoglossidae, 

 Mormyridae, Notopteridae, Hyodontidae, and Halosauridae, in 

 which the parietals meet in the middle line, and the other the 



