78 GUIDE TO THE AUSTRALIAN MUSEUM. 



wliich are developed from the sides of the mouth or neck^ 

 Numerous species are found on the coast at Port Stephens after 

 bad weather, and some have been taken by the towing net in Port 

 Jackson. 



GASTROPODA are so termed from the circumstance of their 

 crawling or gliding on the under surface of their body, termed 

 the "foot." They have been divided into four sections : — 1. The 

 rrosobranchiata, which have the gills situated behind the head in 

 advance of the heart, and are always provided with a shell. 

 2. Tlio OpisthobraHchiata in which the position and structure of 

 the gills are variable, but always behind the heart, and in which the 

 body is either naked or protected by a shell, external or concealed 

 in the mantle. 3. The Nucleohranchiata, which have the gills in 

 a tuft at the hinder part of the back, in some cases protected by 

 a shell ; they do not crawl like the ordinary Gastropods, but 

 are found swimming freely in the open sea, like the Pteropods. 

 4. The Pulmonata, or air-breathers, the breathing-cavity of which 

 opens only by a small aperture which can be closed by a valve. 

 These four primary divisions of Gastropods have been variously 

 split up into smaller sections — families, genera, and subgenera. 



PROSOBRANCHIATA.— The family of Muricidce, or "Rock- 

 shells," comprises many of the largest and most beautiful shells 

 hitherto discovered, often remarkable for the delicacy of their 

 sculpture and the variety of their colours. They are all 

 carnivorous, feeding chiefly on other Mollusca, boring through 

 the shells of bivalves with their spiny tongue, and slowly devour- 

 ing the unfortunate inhabitant piecemeal. From one species found 

 in the Mediterranean (Murex hrandaris), the ancients manu- 

 factured the celebrated Tyrian purple dye : specimens of these are 

 exhibited in the case. The family of Buccinidce contains a very 

 large and various assemblage of forms. Among them may be 

 mentioned the Whelks {Buccinum), and the " Purples " [Purpura) 

 found between tide marks. Magilus is found among the coral-reefs 

 of the Solomon Islands and Mauritius, and has the remarkable 

 habit of lengthening the aperture of its shells into an elongate 

 tube, in order to keep pace with the growth of the coral, and 

 so prevent its being overgrown and killed. 



