_Trachicephalus uranoscopus._ 456 _Chlarias breviceps_, African Catfish. 457 _Notropis whipplii_, Silverfin. 457 _Gymnothorax moringa._ 458 _Seriola lalandi_, Amber-fish. 458 Geological Distribution of the Families of Elasmobranchs. 459 "Tornaria" Larva of _Glossobalanus minutus_. 463 _Glossobalanus minutus._ 464 _Harrimania maculosa._ 465 Development of Larval Tunicate to Fixed Condition. 471 Anatomy of Tunicate. 472 _Ascidia adhærens._ 474 _Styela yacutatensis._ 475 _Styela greeleyi._ 476 _Cynthia superba._ 476 _Botryllus magnus_, Compound Ascidian. 477 _Botryllus magnus._ 478 _Botryllus magnus_, a Single Zooid. 479 _Aplidiopsis jordani_, a Compound Ascidian. 479 _Oikopleura_, Adult Tunicate of Group Larvacea. 480 _Branchiostoma californiense_, California Lancelet. 484 Gill-basket of Lamprey. 485 _Polygnathus dubium._ 488 _Polistotrema stouti_, Hagfish. 489 _Petromyzon marinus_, Lamprey. 491 _Petromyzon marinus unicolor_, Mouth Lake Lamprey. 492 _Lampetra wilderi_, Sea Larvæ Brook Lamprey. 492 _Lampetra wilderi_, Mouth Brook Lamprey. 492 _Lampetra camtschatica_, Kamchatka Lamprey. 495 _Entosphenus tridentatus_, Oregon Lamprey. 496 _Lampetra wilderi_, Brook Lamprey. 505 Fin-spine of _Onchus tenuistriatus_. 509 Section of Vertebræ of Sharks, showing Calcification. 510 _Cladoselache fyleri._ 514 _Cladoselache fyleri_, Ventral View. 515 Teeth of _Cladoselache fyleri_. 515 _Acanthoessus wardi._ 515 _Diplacanthus crassissimus._ 517 _Climatius scutiger._ 518 _Pleuracanthus decheni._ 519