I70 



ZOOLOGY 



1100 species have been described from Devonian rocks. Since 

 this epoch they have dwindled, and at the present day not 

 more than about 100 species exist. 



Argiope (Cistella) neapolitana is a small Brachiopod found 

 attached by a peduncle to pieces of rock at a depth of about 70 

 metres in the Mediterranean. The dorsal and ventral shells 

 entirely cover the body except the peduncle, which projects 

 through a " beak " formed by the ventral or larger shell. The 



Fig. 107. — A longitudinal vertical median 

 section through Argiope neapoUtana. 



1. Ventral shell. 



2. Canal containing blood-vessel. 



3. Sub-oesophageal nerve ganglion. 



4. Mouth. 



5. Stomach. 



6. Peduncle. 



7. Plexus of blood-vessels. 



8. Median crest on dorsal shell. 



9. Organic membrane which has separated 



from shell during the process of de- 

 calcification. 



--6 



dorsal shell is rather the smaller; both are of a brownish hue 

 with small white spots. The body of the Argiope lies almost 

 entirely in the dorsal shell (Fig. 107), and is supported by 

 certain ridges which this shell bears on its inner surface. The 



