BRACHIOPODA. 55 



only one survives (T. vitrea), an inhabitant of the Lusitanian 

 province. The Waldheimias, or Terehratulce with long loops 

 (fig. 11), are widely distributed in our present seas, although 

 only nine living species are known ; individuals of one or 

 more of these are found on the coast of Spitzbergen and Lab- 

 rador, at Cape Horn, and most abundantly in New South 

 Wales and New Zealand : there are sixty fossil species dating 

 from the trias. The Terehratellce, having the loop fixed to a 

 mid ridge, commenced in the lias, occur in small numbers 

 throughout the cretaceous and tertiary periods, and are the 

 only lamp-shells which attain their climax in recent seas. 

 Five species of Argiope occur in the greensand, chalk, and 

 tertiaries. The allied genus Thecidium is represented by one 

 species in the carboniferous and one in the triassic system, 

 becomes comparatively common in the secondary period, and 

 dwindles again to a single species in the newer tertiary ; this 

 species survives within still narrower limits in the Mediter- 

 ranean Sea. The sub-genus Terebratulina is represented by 

 twenty species in the secondary and tertiary formations. T. 

 striata of the chalk is so like the recent T. caput serpentis 

 as to be with difficulty distinguished from it. Several extinct 

 sub-genera occur in the cretaceous strata, of which the most 

 remarkable are Trigonosemus (fig. 12, i) and Lyra, shaped 

 like a violin. The genus Stringocephalus (fig. 12, *) is 

 peculiar to the Devonian strata, and has a large internal loop, 

 and a very prominent cardinal process, forked at the end, 

 and fitting over the central plate of the opposite valve. 



The shell of Terebratula and some of its allies (Argiope, 

 Thecidium, Oyrtia, and Sjpiriferind) is dotted with minute 

 quincuncial perforations, sometimes visible to the naked eye, 

 as in T. lima, but usually requiring a lens of low power. 

 They are smallest in T. carnea. 



The lamp-shells with sharp beaks and plaited valves have 

 been separated from the Tercbratuke under the name Rhyn- 



