DEVELOPMENT OF THE ARMS. 9') 



The harvsG figured on this pl.-ite (IM. III.) cf)rre.'^pon(l to the larvae 

 observed by Van Beneden, and called by him Hrachina ; the latter resem- 

 ble more our larvae than any figured by Midler, 1 am strongly inclined 

 to believe tliat Van Beneden's Brachina ^^ill eventually prove to be the 

 larvae of the Asteracantliion rubens M. 7\, or o£" a closely allied species. 

 The more advanced specimens of his Brachina began to show signs of 

 the brachiolar appendages, though Van Beneden did not notice them. 

 See Fiff. 8 of the Plate accompanying his notice in the Bulletin de 

 I'Academie des Sciences de Belgique for 1850. The.se larvae are easily 

 distinguished from ours by the shortness and thickness of the arms, a.s 

 well as the less elongated shape of the larva. The time of breeding is 

 also different; the European species spawning during the end of March 

 and beginning of April. The A. berylinus spawns in the last part of 

 July; by the 26th no eggs could be found in any of the female.^, and 

 the other species (the A. pallidus) spawns during the third week in 

 August. These facts are additional proofs of the specific difference be- 

 tween our species of Asteracantliion and the Asteracanthion rubens of 

 Europe. 



[I have retained in this memoir the specific names adopted in 1863. 

 At that time no description had been published of Stimpson's A. vulgaris ; 

 his name has subsequently been adopted by writers on American Starfishes, 

 although the figure given on PI. VIIL, had it been baptized and described 

 as a new genus and species, and subsequently proved to be the young 

 of A. vulgaris, would have obtained precedence ; but failing to give it 

 the mythical diagnosis, this memoir was not entitled to recognition by 

 the strict rules of systematic zoology ! 



It is only comparatively recently that A. berylinus r^nd A. arenicola 

 of Stimpson have both proved to be probably identical with A. Forbesii 

 of Desor, so that the name of pallidus would at any rate have to give 

 way to that of Desor.] 



When seen in profile (PI. III. Figs. 9, 12, w, ww ; PI. IV. Fig. 4, v, mr), 

 the water-system runs in an arch, from the alimentary canal to the opening 

 of the mouth ; here the diameter increases, forming a reservoir (/<•//•'), 

 from which are sent off small pouches (/'/')? le^'^tliiig i»to the braiiiiolar 

 arms (//); the whole of the oral opening is placed below the water- 

 system. When seen from above or below (PI. 111. Figs. 6, 8. 10, 11; 

 PI. IV. Figs. 1, 2; PI. VII. Fig. 8) the water-system is an elliptical ring 



