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Show Division 2. B atoidei. Family 1. Rhinobaticlce. a. Pristince-Sclerorhynchus, Propristis, Pristis. b. Rhinobatince-Rliynchobatus, Rliina, Rhino-batus, Discobatus, Trygonorhina, Astrodermus. Family 2. Raiidce. Raia, Psammobatis, Sympterygia, Cyclobatis. Family 3. Dasybatidce. Xiphotrygon, Pteroplatea, Urolophus, Dasybatis, TJrogymnus, Ptychodus, Mylio-batis, Aetobatis, Rhinoptera, Dicerobatis, Ceratoptera, Ceratobatis. Series II. CHASM A TOPNEA. Order HOLOCEPHALI. Family 1. Pyctodontidce. Pyctodus, Rhynchodus, Palseomylus. Family 2. Squalorctiidce. Squaloraia. Family 3. Myriacanthidce. Myriacanthus, Chimseropsis. Family 4. Chimceridce. Ganodus, Ischyodus, Edaphodon, Elas-modus, Rhinochima?ra, Harriotia, Callo-rhynchus, Cliim?era. I am of the opinion that any attempt to apply the rule of priority to the nomenclature of groups such as suborders, orders, &c., unless it is convenient to do so, cannot succeed. To call the Notidanoidei either Paheonotidani, Diplospondyli, or Opistharthri is to give a misleading idea of the characteristics of the division. 7 2 4 m r . c. t a t e r e g a n o n [June 19, Although the Selachians may quite well be regarded as a subclass of the Pisces, it is not improbable that they will be generally accepted as constituting a class distinct from the true Pisces (Teleostomi) when their characteristic peculiarities are more widely known. The Selachii * may be thus defined :- Craniate vertebrates with jaws. Nasal organs paired blind * In the definition and classification o f the Selachii I have left out o f account the Hetevostraci and theii supposed allies, primitive fishes o f Palteozoic times, as to whose positiou iu the system no two authors seem to agree. |