122 GUIDE TO THE FOSSIL INVEETEBEATE ANIMALS. 



Gallery 

 VIII. 

 Case A5. 



Case A5. 



Wall-case 

 12A. 



north, while there was free communication with the seas to 

 the south. The Museum possesses the specimens used by 

 Busk in writing his monograph on the " Crag Polyzoa," and 

 many of them are exhibited. The most interesting forms 

 found in the Crag are some massive Cyclostomes, including 

 the three species known as Alveolaria semiovata, Fascimlaria 

 aurantiitm, and F. tuhipora. Among the Cheilostomes, the 

 most remarkable forms are two species of Cellaria [Sali- 

 cornaria] and one of Melicerita. The numerous species of 

 Scliizoyorella, Mucronella, and Memhranipora are closely allied 

 to or identical with living forms. 



A small collection of Pleistocene species from the Clyde 

 and from Selsea Bill is shown ; but all these species still 

 live on the English coast. 



The Bryozoa from foreign localities are not yet com- 

 pletely arranged, and only a few representative species are 

 exhibited. The lovrest slope of the wall-case is devoted to 

 the Palaeozoic faunas, chief of which are those from the 

 Ordovician and Silurian rocks of North America. The 

 Carboniferous fauna of the same continent furnishes some 

 remarkable forms, notably Archimedes Wortheni, which is 

 like a Fenestella twisted into a screw, and Evactinopora 

 quinqueradiata, another Cryptostome with a star-shaped 

 colony. 



A collection from the Bathonian deposits of Northern 

 France on the middle slope contains several interesting 

 forms, notably Memhranipora jicrassica and Onycliocella 

 flabelliformis, which are the oldest true Cheilostomes known 

 (Fig. 65). 



Among the Tertiary Bryozoa on the top slope, the large 

 specimens from the Miocene deposits of the Mediterranean 

 are most worthy of notice. 



The Trustees have published a Catalogue of the Jurassic 

 Bryozoa (1896), and the first volume of a Catalogue of the 

 Cretaceous Bryozoa (1899), both by Dr. J. W. Gregory. 



MOLLUSCA. 



G-allery 

 VIII. 

 West side 

 and 

 G-allery 

 VII. 



These animals derive their name from their soft bodies 

 (mollis, soft), which never have any internal skeleton, and 

 rarely any hard appendages capable of preservation as fossils. 

 The glandular skin, however, usually secretes, on a portion of 

 the outer surface called the mantle, a hard shell, sometimes 

 horny in appearance, but usually thickened by a deposit of 



