254 SUMMARY OF CURRENT RESEARCHES RELATING TO 



This form of pedicellaria constitutes, perhaps, an urticating organ, or, 

 as Sladen believes, secretes mucus. 



The various statements as to the striation or non-striation of the 

 muscles of Echinoderms are explained by an examination of those of 

 Echinus, in which both conditions may be found in the same muscle 

 at different times ; sometimes even the same fibre is striated in one 

 part and not in another. The presence of striee is coincident with 

 that of constrictions of the fibres, and it is probable that it is con- 

 nected with their contraction. 



New Asteroidea.* — Professor Perrier has a note on the starfishes 

 collected by the steamship ' Blake,* and entrusted to him for description 

 by Professor Alex. Agassiz. Some of these, such as the curious 

 Hymenodiscus, he has already described. Goniojjeden would seem, in 

 the structure of its skeleton, to belong to the Goniasteridse, but the 

 form of its ambiilacral tubes and the characters of its " teeth " are 

 exactly those of Astropeden. Four species of this genus have been 

 distinguished. Badiaster (taken at a depth of 1800 m.) is a large 

 Asterid, which has the spines of Solaster, the marginal plates of 

 Goniaster, and the ventral plates resembling those of some Asterinidce. 

 Ctenaster, which is three-tenths of a metre in diameter, and specimens 

 of which were taken from a depth of 3500 m., has six arms, and 

 resembles a gigantic Ctenodiscus deprived of its ventral plates, and so 

 far resembling the Ediinasteridce. Marginaster is a genus formed for 

 small pentagonal creatures, which resemble Asterina, but have Gonias- 

 terine marginal plates. 



Archaster is very numerously represented, for there are of it seven 

 species, one of which, A. mirahilis, is very variable in form, and is 

 represented by more than one hundred specimens. There are eleven 

 species of Goniasteridoi ; the new genus Anthenoides is intermediate 

 between Anthenea and Pentagonaster. 



Several new forms of pedicellarise, an organ which, as is well 

 known, has been the especial object of M. Perrier's studies, were dis- 

 covered. Pentagonaster ternalis has three, instead of the ordinary 

 two branches. Luidije with four have been foimd. Ardiaster 

 mirahiUs has on some of its ossicles a complicated " comb " of spines, 

 and is interesting as proving the homology of the pedicellariae with 

 the spines, or even the large calcareous granules of the skeleton of 

 Asterids or Echinids. 



A remarkable agreement between the number of the tentacles, 

 the structure of the mouth, and the form of the pedicellariae would 

 seem to lead to the division of the Asterida into two distinct families. 



M. Perrier's very short notice is sufficient to prove that a very 

 considerable addition is being made to our knowledge of these forms. 



Structural Feature, hitherto unknown among EcMnodermata, 

 found in Leep-sea Ophiurans.t— Professor Lyman describes two new 

 genera, OpluothoUa and Ophiohelus, which are characterized by the 



* Cnraptes Rendus, xcii. (1881) pp. 59-61. 



t Auuiv. Mem. Boston Soc. N:it. Hist. (1880) p. 1. 



