34 DEEP-SEA FISHES OF THE ATLANTIC BASIN. 



Order MALACOPTERYGII. 



Symplectic present. No interclavicles. A mesoeoracoid arch. Anterior vertebra sim- 

 ple. No Webberian ossicles. Pharyngeal boues simple above and below, the lower not 

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



KEY TO THE DEEP-SEA FAMILIES. 



Mesoeoracoid well developed as a bridge between the hyper- and hypo-eoracoid. (Gill.) 



I. No barbel and no photophores. Maxillaries form margin of upper jaw. 



A. Adipose tin absent. Body sealy. 



1. Dorsal tin similar to ami opposite anal. No air-bladder ALF.roCEriiAi.mi: 



2. Dorsal fin similar to and opposite anal. Air-bladder present Pterotiiuissid.i; 



B. Adipose tin present. 



1. Gill membranes separate and free from isthmus. Stomach csecal. 



a. Branchiostegals, (> or more Arcentimiu. 



b. Bianchiostegals, 4 or less Mkrosto.mio.e 



2. Gill membranes joined, forming broad bridge across isthmns; gill cavity closed bebind. 



a. Ventrals opposite posterior end of dorsal Batiiylaoid.e 



Mesoeoracoid wanting or atrophied. (Gill.) 

 I. Post-temporal connected with back of cranium near sides. No pliotophorcs or barbel. 



A. Adipose fin typically present. 1 Body not very elongate. Anal distinct. 



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

 a. No photophores. Teeth cardiform, usually hinged. 



i. Maxillary narrow or rudimentary. Hypocoracoids not divergent Synodon i ih.e 



II. Maxillary dilated behind. 



* Pectorals normal. Hypocoracoids divergent - Aui-opih i. 



** Pectorals subliumeral Benthosa turner; 



Pectoral rays elongate, in two groups BatiiyI'TERoiiu 



B. Adipose tin absent. 



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



a. Xo photophores on the scales, but a large, luminous, cephalic plate. 

 1. Maxillary dilated behind. 



* Pectorals and \ cntrals well developed, approximate Il'Nopm.r. 



2. Body scaleless. 



a. Teeth granular, in bands. Pectorals normal. 



i. Ventrals present. < Opercular apparatus incomplete Eondeletiil-.e 



II. Ventrals absent. Opercular apparatus complete; a conspicuous lateral furrow. 



Cetci.mi.miii.i; 



II. Post-temporal impinging upon occiput. 

 * Vertebra' and neural spines normal. 



A. Photophores present, barbel absent. 



1. I'scudobranebia' present. 



a. Premaxillaries forming margin of upper jaw. Bodysealy MyCTOPHIMI 



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



cular apparatus incomplete Maukolicip.e 



2. Pseudobranchiaj absent. Month large, with strong canines. Scales deciduous. 



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



ClIAri.IolMlMin.E 



b. Dorsal bebind ventrals. Anal long. Operculum well developed GONOSTOMIDiE 



B. Photophores and barbel both present. 



1. Maxillaries forming lateral margin of upper jaw. 



a. Adipose iin present. Pectorals present. 



I. Body naked. Dorsal behind vent, but in advance of anal A.sti.-onesthid.f 



b. Adipose tin absent. Pectorals usually present (absent in I'hotonectes) Stomia him; 



2. Premaxillaries only forming margin of upper jaw. 



a. Pectorals rudimentary. Opercula membranaceous. 



i. Body scaleless. Dorsal short, postmedian Malacostf.id.e 



C. Photophores and barbel absent. 



1. Premaxillaries forming margin of upper jaw. Fang-like teeth in mandibles and palatines 

 and sometimes on vomer, 

 a. Dorsal long, occupying entire back. Body naked Alepisaurid .e 



■Absent in Senthosaurus and sometimes in Bathysaurus. 



