678 ACALEPHS. 



the rounded stem have perforations in their cavities by which 

 they can be strung as beads, "which," says Dr. Buckland, 

 (Bridgewater Treatise,) "caused them in ancient times to be 

 used as rosaries." In the northern parts of England, they are 

 still called "St. Cuthbert's beads." They are also known by 

 the name of Wheel Stones. 



The Pentacrinus Europceus, found in the Irish coast, is now 

 considered to be the young of the Rosy-feathered Star-fish, Com- 

 alula. (See Chart.) 



The P. Briareus, (see Chart,) is a fossil species, having great 

 length of stem and numerous side-arms, whence the specific 

 name. It is frequently found in contact with masses of drifted 

 wood. (See PI. XVIII.) 



The PEAR-SHAPED ENCRINITE, Apiocriniles, (Gr. apion, a pear,) 

 rotundus, is so named from the form of its body. The figures 

 on the Chart represent it with its expanded and closed arms. It 

 is fixed by a jointed peduncle. The surfaces of the joints of the 

 vertebral column are striated with rays. 



The Pentacrinites have pentagonal stems, and are found in the 

 more recent strata. Besides the species found in the Bay of 

 Cork, above referred to, a larger one, Holopus, (Gr. holos, whole ; 

 pous, foot,) rangei, is found in the West Indian seas. 



SECOND CLASS. ACALEPHS, (Gr. oxalifo?, akaUplie, a nettle.) 



This class derives its name from the stinging power possessed 

 by a large portion of the animals composing it, and sometimes in 

 so high a degree as to be a terror to bathers. They are known 

 by the names SEA-NETTLES, MEDUSA, SEA-JELLIES, &c. Having 

 the power of free motion, they float in all seas, especially those 

 of the warmer latitudes. They are not like the Echinoderms, 

 enclosed in a thick integument ; but, on the other hand, one of 

 their most striking peculiarities is their extreme softness. Some 

 of them attain considerable size, but almost all are without any 

 internal support or skeleton. Their soft tissues give them the 

 appearance of a mass of jelly, a mere net work of animal fila- 

 ments, the intermediate spaces of which are filled up with sea- 

 water. Hence, although some of the largest reach the size of 

 two feet, and a weight of fifty or sixty pounds, yet, when they are 

 dried, the pounds become grains. Many of the Medusse are ex- 

 tremely beautiful, reflecting the prismatic rays. DeBlainville 

 represents their form as "nearly always circular, sometimes dis- 

 coidal or spheroidal, but most frequentlv hemispherical." 

 They quite commonly have a form like that of our umbrellas; 



