HARD WICKE 'S S CIENCE - G O SSI P. 



135 



between the extreme north of Scotland 

 and Iceland, is known to belong per- 

 haps to the same genus as that found 

 fossil in our chalk strata, and called 

 Bonrgetocrimis. Now this recently- 

 discovered genus of living Crinoids has 

 been well examined, and much light 

 has consequently been thrown upon 

 the structures of fossil Encrinites of all 

 ages. 



Cuvier, and many naturalists after 

 him, including even Agassiz, grouped 



the Encrinites among that hodge-podge 

 Fig. 130. c. Detailed plates which compose test oi Peiitreviites ; d. Upper surface /- ■ i • . .-n n i t-> j- ^ 



of P^^Z/rw/^.'^, showing ambulacra! furrows. of marme objects Still Called A«<//rt^.Z. 



This term is about as expressive of any 

 real facts or mutual relationships as 

 the names of the orders and classes of 

 plants under the Linnean system of 

 botany are to the plants themselves. 

 The order Radiata is a kind of zoo- 

 logical "lumber-room," into which all 

 kinds of little or not understood crea- 

 tures were thrust, if they only had ra- 

 diating organs around the mouth ; or 

 even if the body itself was of a stellar 

 or radiated shape, as in the case of 

 the star-fishes. The Radiata is no 

 longer used by modern naturalists, and 

 most of the animals, living and extinct, 

 formerly grouped under that name, have 

 been assigned to distinctive and clearly- 

 understood groups. 



Thus, all the spiny-skinned animals 

 {Echinodermata) are now included in 

 the %vi^-V\x\^Ao\xs. Amitdoida, or "ring- 

 like " animals. All are internally re- 

 lated, although their external shapes 

 may be different, by the possession of a 

 peculiar apparatus called the ' ' water- 

 vascular system." In the Sea-urchins 

 and common Star-fishes this highly- 

 developed hydraulic machinery is im- 

 mediately applied to locomotive pur- 

 poses ; and these creatures are thereby 

 enabled to move about over the sea- 

 floor. In the Crinoids, the water- 

 vascular system is perhaps employed 

 for respiratory purposes. But, even 

 in the shapes of the Echinodermata, 

 varied though they be, we can pass almost imper- 

 ceptibly from one type to another. Thus, we might 

 begin with living Encrinites, such as the Rhizocriniis 

 of northern seas, the rare and beautiful Feniacrinns 

 Capitt-Mcdnscc of West Indian seas, nearly related 

 to the abundant species {P. hriareits) found in the 

 Lias, and the little Pentacrimis Enropanis, occa- 

 sionally dredged up in quiet spots off the southern 

 coasts of Ireland. The latter has a jointed stem, 

 and is usually attached to Sertularians. It is now 



Fig. 131. Pentacriiius briarens. a, common Liassic Encrinite ; /', upper 



surface of body. 



species of Encrinite is, no matter what shape the 

 latter may assume. But the history of Encrinites has 

 been involved in a good deal of obscurity, from which 

 it is now emerging. This was partly due to the 

 fact that, a few years ago, few or no real Encrinites 

 were known to be in existence; and none had 

 been thoroughly dissected. The dredging expeditions 

 of Carpenter, Wyville Thomson, and others, Ibrought 

 to light several species. One called Rhizoerinus lo/o- 

 tenesis, found living in the deeper parts of the sea, 



