152 



LOWEi: !j\VJ:1!TEIJIIA te.s. 



powerful muscular action called for in the rapid whip-like motion of the arm. O. 

 lineata occurs in Florida, and three or four species are found in southern and Lower 

 California. Ophiociasma uttenuatum is a curious form found in the South Atlantic. 

 The examples taken had si.\ arms, the disc is covered with thick soft skin, and the 

 arms, which are very long and slender, have the lower and side plates inijicrfectly 

 calcified, and no upper plates. The spines are short, three on each joint. The two 

 known sjiecies of OpJdohelm are remarkable for the curious minute sj^ines or pedicel- 

 lari», havinij the form of a long-handled parasol, that take the place of the true arm- 

 spines on the outer ami-joints. One of the most singular of ophiurans is 0]?]iiothelia 

 supplicans, in which the disc is sliajied like a high sugar-loaf, and the arms can bo raised 

 upwards. The arms bear upon all the joints beyond the ninth a cluster of three or 

 four niinute parasol-like jiedicellariiB, set a little inside the true arm-spines, which con- 

 tinue to the end of the arm. The under surface of the disc is curiously ornamented. 

 A frill of long, flat, curved jiajiillw is set upon each mouth-angle, which, ending in- 

 wardly in a sharp tooth, resemble so many birds' heads with a pointed bill. Externally 

 to the mouth pajiillje are three ])arallel rows of regular club-shaped flat jiapillie. This 

 form is only known from south-west of Juan Fernandez, and was taken at a depth of 

 one thousand eight hundred and twenty-five fathoms. Ophi/omi/ces has a very pecu- 

 liar arrangement of mouth jiajiilL'e, and two of its s]iecies occur between five liundred 

 and one thousand fathoms. 



Two or three genera of Ojihim-ida- contain sjiecies with cylindrical arms, while the 

 entire animal is clothed with a thick skin, and the arm-})lates are imperfectly developed. 

 They thus approach the Astro])hytid;e. In Op/iiobi/rsa rudis, which was taken 

 off the entrance to Port Philij), in thirty-eight fathoms, each arm is about twelve 

 inches long, though the disc measures only about an inch. 



UphUmiyxa vivijKira is, as the name imjjlies, a viviparous species. 



The best known genus of Asteophytid.b is Astrop/ii/ton itself, of which seven 

 species are known. Though there are no arm-s])ines, the outer brandies of the arms 

 have s])ine-like tentacle scales. The long bar-like radial shields of the disc are covered 

 by the thick skin, but show as elevated radiating ribs reaching to its centre. Under 

 the skin of the arms there are side arm-i)lates, which cover the lower side of the arms, 

 but there is only a basal under arm-i)late, and there are no up])er ai-m-])lates at all. 

 Gorgoiwcejihalus has also branching arms, but the plates under the skin of the disc 

 are differently arranged, and the arms, wide at their base in AstropJu/ton, are here 

 narrow, while the forkings are less numerous than in that genus. The young has at 

 first a flat disc covered with jilates like that of an ordinary oi)hiuran, this first becomes 

 covered a close granulation ; then both the granulation and the disc-])lates atrojjhj', 

 except those of the margin, which continue to grow and multiply ; and finally the 

 radial shields acquire their great length and height. In Euryale no ]>ro]ier arm-si)ines 

 are pi-esent, and in Astroclon and Tric/iaster the forks are but few. The total length 

 of an arm of T. propuffnutoris is about sixteen inches. Among the Astro] ihytidre with 

 unbranched arms the principal genus is Astroc/ienia, ^v\uch has well-formed under arm- 

 plates like an o])hiuran. Ophiocreas ahijssicola was taken in twenty-three hundi'cd 

 fathoms. 



Order 11. — ASTEROIDEA. 



The differences which distinguish the star-fishes from the ophiuroids are scarcely 

 less imjiortant than those which separate either from the sea-urchins, yet the external 



