210 



HISTORICAL PALAEONTOLOGY. 



istic of the Muschelkalk. In this beautiful species, the flower- 

 Hke head is supported upon a rounded stem, the joints of 

 which are elaborately articulated with one 

 another; and the fringed arms are com- 

 posed each of a double series of alter- 

 nating calcareous pieces. The Palaeozoic 

 Urchins, with their supernumerary rows of 

 plates, the Cystideans, and the Pentremites 

 have finally disappeared : but both Star- 

 fishes and Brittle-stars continue to be rep- 

 resented. One of the latter — namely, the 

 Aspiduraloncataoi GdidiViSS (fig. 143) — is 



Fig. 143. — Aspidura loricata, a Triasbic Ophiuroid. 

 Muschelkalk, Germany. 



highly characteristic of the Muschelkalk. 



The remains of Articulate Animals are 

 not very abundant in the Trias, if we except 

 the bivalved cases of the little Water-fleas 

 {Ostracoda), which are occasionally very 

 plentiful. There are also many species 

 of the horny, concentrically-striated valves 

 of the EsthericB (see fig. 122, b), which 

 might easily be taken for small Bivalve 

 ]\Iolluscs. The ''Long-tailed" Decapods, 

 of the type of the Lobster, are not with- 

 out examples, but they become much more 

 numerous in the succeeding Jurassic pe- 

 riod. Remains of insects have also been discovered. 



Amongst the Mollusca we have to note the disappearance, 

 amongst the lower groups, of many characteristic Palaeozoic 

 types. Amongst the Polyzoans, the characteristic " Lace- 

 corals," Fefiestel/a, Retepora,'^ Synodadia, Folypora, &c., have 



Fig. 142. — Head and 

 upper part of the column 

 of Enc7-i>ius iiliiforinis. 

 The lo\\-er figure shows 

 the articulating surface 

 of one of the joints of the 

 column. Muschelkalk, 

 Germany. 



* The genus Retepora is really a recent one, represented by living forms ; 

 and the so-called Rcteporce of the Palaeozoic rocks should properly receive 

 another name {Phyllopora\, as being of a different nature. The name 

 Retepora has been here retained for these old forms simply in accordance 

 with general usage. 



