Miscellaneous. 327 



recurved like a sabre, as in the Astropectinidaa. The arubulacrul 

 tentacles arc qnadriserial at the base of the arms, but biserial at 

 the extremity — which is an additional proof how artificial is the old 

 division of the Asterio3 adopted by Midler and Troschel. These 

 tentacles are terminated by a very small sucking-disk, which still 

 further approximates Zoroaster to Luidia ; they are intermixed with 

 small straight pedicellariae (pediceUaires droites) : we may give the 

 same name to some of these organs disseminated between the dorsal 

 plates. The Zoroasteres were brought up by the dredge in sight 

 of St. Kitts, from depths varying between 120 and 321 fathoms. 



The starfish for. which I propose the name of Hymenodiscus 

 Agassizii is still more remarkable. I have examined two specimens 

 which together complete the characters : one is a perfect disk, but 

 destitute of arms ; in the other the arms are well preserved, but 

 the disk is perforated in the centre. They were collected in sight 

 of Dominica, at depths of 321 and 450 fathoms. These are very 

 delicate starfishes, which constitute an intermediate type very 

 differently marked from the celebrated Brisincjce of Asbjornsen. 

 The Hymenodisci, in fact, resemble the Ophiuri in their rounded 

 disk, clearly distinct from the arms, which are slender, elongated, 

 mobile, and provided with a lateral row of spines like those of these 

 animals, and likewise seem to serve only as organs of locomotion. 

 But these arms are twelve in number, while there are never more 

 than seven in the Ophiuri, and very generally only five. The disk 

 is flattened, very thin, and destitute of a skeleton ; so that it is 

 represented only by a transparent membranous circle stretched upon 

 the circlet formed by the whole of the first ossicles of the arms, and 

 almost in contact with the buccal membrane. The stomach has 

 hardly more space for its lodgment than the thickness of a sheet of 

 paper ; and one is puzzled to know what can be the usual food of an 

 animal so constructed. Spicules in the form of fenestrated calca- 

 reous plates, each bearing a small spine, are disseminated in the sub- 

 stance of the dorsal membrane. Through its walls one can clearly 

 perceive the circular canal which surrounds the mouth, and the 

 ambulacral vessels which start from it and penetrate into the arms, 

 terminating at their extremity, and giving origin in their course to 

 only a double row of ambulacral tubes. I have found no trace of 

 the long coecal processes which the stomach sends forth into the 

 arms in all the Stellerida ; and, unfortunately, I have been unable to 

 observe the genital glands in the individuals that I possess ; but 

 from this we must not conclude that these glands are developed in 

 the disk in Hymenodiscus as in the Ophiuri. 



The skeleton of the arms is very simple and of a very peculiar 

 structure. It is formed of four series of pieces. The two median 

 series form the dorsal ridge ; they aro produced laterally into a 

 sort of shield which partially covers the pieces of the two lateral 

 series. The latter alternate with the preceding, and form the 

 border of the ambulacral furrow ; each of them bears in its middle 

 a long lateral spine, covered by a soft sheath, inflated into a club, 

 and having at its apex a tuft of pedicellariae. These are crossed 

 pedicellariae {pediceUaires crois?es), characteristic, as I have shown 

 in previous memoirs, of the great division of the Asteriadas. 



These four scries of pieces form a groove in which the ambulacial 



