CONTENTS. 



CHAPTER XVII. 



PAOB 



01 THE CLASS OF GASTEROPODA 361 



ORDER I. PULMONEA . .... 370 



ORDER II. NUDIBRANCHIATA . ... 373 



ORDER III. INFEROBRANCHIATA , 375 



ORDER IV. TECTIBRANCHIATA . . . . ib. 



ORDER V. PECTINIBRANCHIATA ..... 377 



ORDER VI. TUBULIBRANCHIATA . . . . . . 386 



ORDER VII. SCUTIBRANCHIATA . . . . . . ib. 



ORDER VIII. CYCLOBRANCHIATA 387 



CHAPTER XVIII. 



OF THE LAMELLIBRANCHIATE CONCHIFERA 390 



ORDER I. OSTRACEJE 397 



ORDER II. PECTINIDJE 401 



ORDER III. MARGARITACEJE 402 



ORDER IV. MYTILACE.E 405 



ORDER V. UNIONID* 407 



ORDER VI. ARCACEJE 408 



ORDER VII. CHAMACFJE 409 



ORDER VIII CARDIACE* 411 



ORDER IX. SOLENID.K . . . . . .413 



ORDER X. INCLUSA 414 



CHAPTER XIX. 



OF THE CLASS OF PALLIOBRANCHIATA . 420 



CHAPTER XX. 



OF THK CLASS OF TUNICATA , . . 423 



CHAPTER XXI. 



GENERAL CHARACTERS OF RADIATA ...... 435 



