34 DEEP-SEA FISHES OF THE ATLANTIC BASIN. 



Order MALACOPTERYGII. 



Symplei'tic present. No iutLTclavicles. Amesocorncoid inch. Anterior vertebiiP sim- 

 ple. No Webbonun ossicles. Pharyngeal bones simple above and below, the lower not 

 falciform. Gills four, a slit behind the ftmrth. (Gill.) 



KKY TO THE DEEP-SEA FAMILIES. 



Mcsocoracoid wcU dcrelopcd as a bridge between the hyper- aiid hi/po-coraroid. ((Jill.) 

 I. Nobiirbel and uo jiliotophiiivs. Maxillaiies form margin of npper jaw. 



A. Adipose tin .ibsent. liody soaly. 



1. Dorsal fin similar to and opposite anal. No air-bladder ALEPOCEPII.U.ID.E 



2. Dorsal tin similar to and opposite anal. Air-bladder present Ptkkuthkissid.e 



B. Adipose fin present. 



1. Gill meiubraues separate and free from isthmns. Stomach eieeal. 



a. Brancliiostegals, 6 or more AnGENTiNiD.E 



b. Branch iostegals, 4 or less Microsto.mid.e 



2. GiU membranes joined, forming broad bridge across isthmns ; gill cavity closed behind. 



a. Veutrals opposite po.sterior end of dorsal Batiiyl.vgiu.e 



ilesocoracoid wanting or atrophied. (Gill.) 

 I. Post-temporal connected with back of cranium near sides. No photophores or liarbel. 



A. Adipose fin typically present.' Body not very elongate-. Anal distinct. 



1. Scales present, persistent (in all Atlantic forms). Teeth cardiform or villiform. 

 a. No photophores. Teeth cardiform, nsnally hinged. 



I. Maxillary narrow or rudimentary. Hypocoracoids not divergent Synodoxtid.e 



II. Maxillary dilated behind. 



* Pectorals nonnal. Hypocoracoids divergent Aulopid.'E 



* ' Pectorals subhumeral Benthosaukid-e 



•** Pectoral rays elongate, in two groups Batiiypteroid.e 



B. Adipose tin absent. 



1. Scales large, thin, and deciduous. Teeth villiform, in bauds. 



a. No photojihorcs on the scales, but a large, luminous, cephalic plate. 

 I. Maxillary dilated behind. 



* Pectorals and veutrals well developed, approximate Ipnoimd.E 



2. Body scaleless. 



a. Teeth granular, in bands. Pectorals normal. 



I. Veutrals ]>rcsent. Opercular apparatus incomplete Rondeletiip-E 



II. Veutrals absent. Opercular apparatus complete; a' conspicuous lateral furrow. 



Cetu.'mimid.e 



II. Post-temporal impinging upon occiput. 

 * Vertebra- and neural spines normal. 



A. Photophores present, barbel absent. 



1. Psendobrauchiie present. 



a. Premaxillaries forming margin of upper jaw. Body scaly Myctophid.e 



b. Maxillary and intermaxillary together forming margin of upper jaw. Body naked. Oper- 



cular apjiaratus incomplete Maui!0LIC1D.e 



2. Psendobrauehia' absent. Mouth large, with strong canines. Scales deciduous. 



a. Dorsal in front of veutrals. Anal short. Canines immense. Operculum incomplete. 



Cn.\rLi()i)()N'Tii).E 



b. Dorsal boliind veutrals. Anal long. Operculum well developed Go>'osTo.MII).E 



B. Photophores ,and barliel liotli present. 



1. Maxilhiries forming lateral margin of upper jaw. 



a. Adipose fin present. Pectorals present. 



I. Body naked. Dorsal behind vent, but in advance of anal A.stroxesthid.f 



b. Adipose fin absent. Pectorals usually present (absent in I'hotonectes) Stomiatid^e 



2. Premaxillaries only forming margin of upper jaw. 



a. Pectorals rudimentary. Opercula membran.aceous. 



I. Body scaleless. Dorsal short, postmedian Maxacosteid.e 



C. Photophores and barbel absent. 



1. Premaxillaries forming margin of upjier jaw. Fang-like teeth in mandibles au<l jialatines 

 and sometimes on vomer. 

 a. Dorsal long, occupying entire back. Body naked AiKPisAfKiD.E 



'Absent in JienthosaiiriiK and sometimes in liathiisaurus. 



