380 ZOOLOGY SECT 



oral surface the comparatively broad, flat surfaces between the 

 ambulacral grooves are roughish, owing to the plate-like ossicles 

 being beset with a number of minute rounded tubercles or granules, 

 which, in the immediate neighbourhood of the ambulacral 

 grooves, assume the character of short, blunt spines. Here and 

 there among the tubercles, usually one in the middle of each 

 ossicle, are pedicellarice, which differ widely from those of Asterias. 

 Each pedicellaria in Anthenea is a small, narrow, oblong, calcareous 

 body, consisting of two parallel narrow valves or jaw r s : these, 

 instead of being supported on a flexible stalk, are articulated with 

 the edges of a slit-like depression on the surface of the flat ossicle, 

 and are thus on a level with the general surface. The term valvate 

 is applied to pedicellarise of this description. In a living Anthenea 

 many of the pedicellariaj will be found to have their valves widely 

 open ; when they are touched the valves close together, gradually 

 opening again after a little time. The ambulacral spines bounding 

 the ambulacral grooves are flattened and blunt, and arranged 

 in fan-like fasciculi. Round the border separating the aboral and 

 oral surfaces the plates are arranged in two somewhat irregular 

 rows. 



The aboral surface is strongly convex, but not uniformly so, there 

 being a more or less distinct depression in the form of a shallow" 

 open groove, the inter-radial depression, opposite each of the intervals 

 between the arms. The surface is dotted over with numerous small 

 rounded tubercles, arranged in somewhat irregular radiating lines. 

 These aboral tubercles, though fewer than those on the oral surface, 

 are for the most part more prominent, so that they assume the 

 character of short spines. The ossicles on which they are borne 

 are star-shaped with six rays, a spine being borne in the centre of 

 each ossicle, and one on each of the rays. Between the ossicles the 

 surface is covered with a soft, slimy skin, perforated by a large 

 number of minute dermal pores, each of which is enclosed by a 

 minute irregular ring of calcareous matter ; each pore serves for 

 the lodgment of one of the dermal branchia3. Numerous pedi- 

 cellariaa, similar to those on the ventral surface, but smaller, are 

 borne on the ossicles, usually taking the place normally occupied by 

 the central spine. The tube-feet are arranged in a single row on each 

 side of each ambulacral groove ; but the ampullce are in two rows, 

 an upper and a lower, and each tube-foot has two ampullae connected 

 with it, one of the upper row and one of the lower row. 



Anthenea has vertical calcareous inter-radial partitions not 

 developed in Asterias. There are five bifid intestinal cceca, which 

 are narrow tubes, slightly enlarged and lobed at the extremities. 



Development of a Starfish (Asterina gibbosa or A. 

 exigua. 1 In these Starfishes the reproductive apertures are 



The development of these has been described in preference to that of the 

 examples, as it is more completely known. 



