INVERTEBRATE ANIMALS. 21 



Group 60. — Family UNIONID^. imio, a pearl. Eiver- 

 mussels. Estimated number of species : recent, 574 ; 

 British, 4 ; fossil, 100. Tertiary. 



IT Examples of Unio, Anodonta, Mycetopus. 



Upper Compartment. 



British Pearls; figures of Bhudda and artificial 



pearls in Unio plicatus. 

 Unio multiplicatus ; extensive fracture repaired in a 



very peculiar manner by the animal ; from the 



Gaskoin cabinet. 



Sktl^ Cabk €Mt^ 



The Mark ^ indicates specimens or other illustrations exhibited in the cases. 



Section SIPHONIDA. a-Kpm, a tube. 

 The presence of a well developed respiratory siphon indicates, gentr- 

 ally, that the species live more or less immersed in sand or mud. 



Group 61. — Family LUCINID^ and allies. Lucina 

 a name of Juno. Estimated number of species : recent, 

 362; British, 17; fossil, 330. From the Devonian 

 upwards. 



^ Illustrations of the genera in the families Un- 

 gulinidce, Laseidce, Leptonidce, Galeommidce, 

 Solemyidce, Astartidce. Fine series of Crassa- 

 tella. 



Group 62. — Family CHAMIDiE and allies, ^ajw-a*, on the 

 ground. Estimated number of species : recent, 52 ; 

 British, ; fossil, 30. From the Chalk upwards. 



IT Chama, Hippopus, Tridacna, Arcinella, Chame- 

 trachcea, dc. Chama Lazarus, very fine. 



Upper Compartment. 



Small example of T, gigas, the largest known mol- 

 lusc ; the shell attains the weight of 500 lbs. 



