Acasta sporillus 319 3. Genus Tetraclita 321 1. Tetraclita porosa 329 Var. communis, nigrescens, viridis, rubescens, elegans, communis (young), patellaris 2. Tetraclita serrata 334 3. Tetraclita rosea 335 4. Tetraclita purpurascens 337 5. Tetraclita costata 339 6. Tetraclita vitiata 340 7. Tetraclita cœrulescens 342 8. Tetraclita radiata 343 4. Genus Elminius 345 1. Elminius Kingii 348 2. Elminius modestus 350 3. Elminius plicatus 351 4. Elminius simplex 353 5. Genus Pyrgoma 355 1. Pyrgoma anglicum 360 2. Pyrgoma Stokesii 361 3. Pyrgoma cancellatum 362 4. Pyrgoma conjugatum 364 5. Pyrgoma grande 365 6. Pyrgoma milleporæ 367 7. Pyrgoma dentatum 369 8. Pyrgoma crenatum 370 9. Pyrgoma monticulariæ 372 Species dubiæ 374 6. Sub-Genus Creusia 375 1. Creusia spinulosa 376 Varieties with the Scuta and Terga calcified together 380 7. Genus Chelonobia 382 1. Chelonobia testudinaria 392 2. Chelonobia caretta 394 3. Chelonobia patula 396 Second Section of the Sub-Family of Balaninæ 397 8. Genus Coronula 397 1. Coronula balænaris 415 2. Coronula diadema 417 3. Coronula reginæ 419 4. Coronula barbara 421 Species Dubiæ 423 9. Genus Platylepas 424 1.