202 



HISTORICAL PALEONTOLOGY. 



scribed, but are of no special importance. Amongst the 

 Crustaceans, however, we have to note the total absence of 

 the great Palaeozoic group of the Trilobites; whilst the little 

 Ostracoda and Phyllopods still continue to be represented. 

 We have also to note the first appearance here of the " Short- 

 tailed" Decapods or Crabs (Brachyura), the highest of all the 

 groups of Crustacea, in the person of Hemitrochiscus paradoxus, 

 an extremely minute Crab from the Permian of Germany. 



Amongst the Mollusca, the remains of Polyzoa may fairly be 

 said to be amongst the most abundant of all the fossils of the 

 Permian formation. The principal forms of these are the 

 fronds of the Lace-corals (Fenestella, Retepora, and Synocladia), 

 which are very abundant in the Magnesian Limestone of the 

 north of England, and belong to various highly characteristic 

 species (such as Fenestella retiformis, Retepora Ehrenbergi, and 

 Synocladia virgulacea). The Brachiopoda are also represented 

 in moderate numbers in the Permian. Along with species of 

 the persistent genera Discina Crania, and Lingula, we still 

 meet with representatives of the old groups Spirifera, Athyris, 

 and Streptorhynchus ; and the Carboniferous Products yet 

 survive under well-marked and characteristic types, though in 

 much-diminished numbers. The species of Brachiopods here 

 figured (fig. 135) are characteristic of the Magnesian Limestone 

 in Britain and of the corresponding strata on the Continent. 



Fig. 135. Brachiopods of the Permian formation, a, Producta horrida; b, Lingula 

 Credneri; c, Perebratula elongata; dand e, Camarophoria globulina. (After King.) 



Upon the whole, the most characteristic Permian Brachiopods 

 belong to the genera Producta, Strophalosia, and Camaro- 

 phoria. 



The Bivalves (Lamellibranchiata} have a tolerably varied 



