120 



CxENtllD AcANTlIOPTEnES.- 



-FISHES.- 



-URANOSCliriANS. 



bone they form being merely tlie substance called 

 "osteoid" by Kullikor. The dermal or exo-skelcton 

 exists generally in form of ctenoid scales, though some 

 Acanthopteres have cycloid scales, and some are desti- 

 tute of scales. The ventrals are situated in the great 

 majority of the order on the thorax, and have a spine 

 in front. The first dorsal, or when that fin is solitary, 

 its anterior rays and the front rays of the anal, are 

 spinous. In many, spinous angles or processes are 

 developed on the cranial or opercular bones, there being 

 a considerable variety of defensive armour exhibited 

 by dilTorent members of the order. Normally the 

 number of branching or jointed rays in the ventrals are 

 five, but there are many exceptions, and some families 

 want ventrals The swim-bladder when present is 



closed. All the fishes of this order have a single giU- 

 opening on each side, generally four pairs of double- 

 ranked gills with free tips, and but one pair of valves 

 at the root of the arterial bulb, guarding the ventriculo- 

 arterial orifice, and no spiral rows of valves in the inte- 

 rior of the bulb. The maxillary bone lies behind the 

 extremity of the premaxillary, and does not constitute 

 any part of tlie upper border of the mouth. 



The first sub-order of Acanthopteres has most gone- 

 rally ctenoid scales, there being only a few exceptions 

 in which the scales are small, tender, and cycloid ; but 

 the other parts of their structure agreeing closely with 

 the ctenoid genera, it has not been thought expedient 

 to separate them. On the limits of the sub-order, 

 genera and species destitute of scales occur. 



SuB-OKDER I.— CTENOID ACANTHOPTERES. 



Family I.— PSEUDOCHROMIDS {Pacxuh- 

 chromidw). 



The members of this group are scaly Acanthopteres, 

 with a long dorsal fin, preceded by a few spines either 

 in a detached fin, or joined to the soft rays by mem- 



brane. Their lateral line is interrupted; the check is 

 not cuirassed by the second sub-orbitar, and there are 

 no sharp serratures or spines on the opercidar bones. 

 Branchiostegals six. 



The family includes the following gonera — Cichlops ; PseJi' 

 dochromis ; Fseudoplesiops (Bleuker) ; Notoiheuia (Kichar Json). 



Fig 30. 



Leather-headed Notothen (Nototheuia coriiceps). 



Notothcnia is a genus of the high southern latitudes, 

 discovered on the antarctic voyage of Admiral Sir 

 James Clark Ross. 



Family II.— URANOSCOPIANS, or SKY- 

 GAZERS.— (Plate 7, fig. 35.) 



This family group, equivalent to the Trachinidw of 

 P>onapartc, consists of fishes whose ventrals of one 

 spine and five soft rays are situated before the pectorals, 

 or close behind them, and which have either a naked 

 skin, or scales of cycloid structure. The vent is gene- 

 rally before the middle of the fish, so that the tail 



exceeds the body in length. The caudal is distinct 

 from the other vertical fins, and the spinous dorsal is 

 usually abbreviated, and sometimes absent. A pro- 

 jection of the mandible in some genera gives a vertical 

 aspect to the orifice of the mouth, which is always 

 terminal, and is bordered above its angles by tlie pre- 

 maxillaries to the exclusion of the maxillaries. No 

 sharp points or serratures exist on the sub-orbitar or 

 preopercular pieces, but in some cases a strong spine 

 issues from the surface of the operculum or from the 

 shoulder-bone. The branchiostegals generally number 

 six or seven ; more rarely five. Occasionally the 

 cavity of the abdomen is prolonged past the vent into 



