218 CHECK-LIST OF THE FISH AND FISH-LIKE ANIMALS OF NEW SOUTH WALES. 



Finally, I owe much to the Council of the Royal Zoological Society of New South Wales for 

 undertaking the expensive work of publication. 



Keys, and How to Use Them. — Though the accompanying keys may at first sight appear involved, 

 a little practice in their use will prove them to be quite simple. The letters before each section are 

 to be regarded as mere symbols without alphabetical value, which might be replaced by any other set 

 of symbols. The divisions and subdivisions in the keys are always alternative to one another, so thai 

 if a species does not have the characters ascribed to any section denoted by a single letter, it should 

 be compared with those in the alternative section denoted by the same letter in duplicate. Thus, 

 if the specimen does not lit into section A of a key, its characters will probably be found under section 

 AA ; it may then be further restricted by comparison with sections under AA — say, H, for example, 

 and if it is found to differ from the characters there denoted, it should be compared with HH, and so 

 on. The relative insetting of the various divisions of the keys further indicates their alternative 

 characters, and also serves as a guide to the subdivisions included within them. 



Key to the larger divisions of the Fish-like Animals. 



A. Cranium wanting. LANCELET. Subphylura Acrania or Cephalochordata (No. I only), 



AA. Cranium present. Subphylum Craniata or Vertebrata (No. ii. and onward). 



B. Nasal apparatus single and median ; no lower jaw. LAMPREY. Class Cyclostomata (No. ii. only). 



BB. Nasal apparatus paired ; lower jaw present. 



C. Skull without (Plagiostomi) or with only a rudimentary [Holocephali) operculum ; 



males with paired intromittent organs. SHARKS and RAYS. Class Elasmobranchii (N'os. iii.-xxv.). 



CC. Skull with an operculum on each side ; males without 



paired intromittent organs. FISHES. Class Pisces (No. xxvi. and onward). 



LANCELETS. Subphylum ACRANIA or CEPHALOCHORDATA. 



I. Family Branchiostomidae. 



i. Epigonichthys Peters, Monatsb. Akad. Berlin, 1876, p. 325 (cultcllus). 



ia. E. bassanus. Lancelet. Branchiostoma bassaniim, Gunther, Voy. Alert, Zool., 1884 

 p. 31; Heteropleuron bassanum Kirkaldy, Quart. Journ. Micr. Soc. (n. ser.), xxxvii, 1895 

 P- 3'4. pl- 34. '' (PI- xvi). 

 A small semitransparcnt, marine animal, about ij inches long, which has no back-bone. It burrows 

 in sand. 



BACK-BONED ANIMALS. Subphylum CRANIATA or VERTEBRATA. 

 LAMPREYS and HAG-FISHES. Class CYCLOSTOMATA 

 II. Family Mordaciidae. 



2. Mordacia Gray List Fish. Brit. Mus., Chondropt., 1851, p. 143 [mordax). 



2a. M. mordax. Short-headed Lamprey. Petromyzon mordax Richardson, Ichth. Erebus 

 and Terror, 1846, p. 62, pl. 38, 3-6 (PI. xvi). 



An eel-shaped animal with a suctorial mouth armed with horny teeth by means of which it rasps 

 holes in the flesh of living fishes upon which it feeds. It is marine in its younger stages but ascends 

 rivers to breed. Rare in New South Wales. 



SHARKS, RAYS AND GHOST SHARKS. Class ELASMOBRANCHII. 



A. Live to seven external gill-openings ; dorsal spine, if 



present not erectile ; teeth numerous. SHARKS and RAYS. Subclass Plagiostomi (Nl s. iii.-xxiv.). 



AA. One external gill-opening ; an erectile dorsal spine ; teeth few. GHOST SHARKS. Subclass Holocephali (Hi .. svv. only). 



