77 



12. Pteraster obscurus (Perriei). 

 Hexaster obscurus Perrier. 



Per rier: Contribution à l'étude des Stellérides de l'Atlantique Nord. 

 Resultats des campagnes scientifiques par Albert 1er, Prince Souverain de 

 Monaco. Fasc. XI. 1896. p. 41. — Döderlein: Op. cit. p. 213. — Ludwig: 

 Op. cit. p. 468. 



Hurry Inlet, 50 fathoms, I specimen. 



13. Pteraster miiitaris (O.F.Müll.). — PI. II. Fig. 4— 5. 



Lût к en: Op. cit. p. 43. — Sars: Op. cit. p. 48. — Duncan&Sladen. 

 Op. cit. p. 46. — Bell: Op. cit. p. 93. — Ludwig: Op. cit. p. 469. 



Turner Sund, 120 fathoms, 1 specimen. 



Duncan & Sladen (Op. cit. p. 47) have pointed out that 

 the secondary mouthspines in Pteraster miiitaris have «the tip 

 abruptly pointed, transparent and glass -Ике», and Sladen makes 

 the same remark (« Challenger »-Asteroidea) for several other 

 Pteraster- s.nd Betaster-&T^ec\e&. Perrier (Mém. sur les Étoiles 

 de mer recueiUis dans la mer des Antilles et le Golf de Mexique. 

 Nouv. Arch. d. Mus. d'hist. nat. 2 Sér. 6. 1884) finds the same 

 structure in Pteraster caribœus. Also in Goniodon dilatatus 

 Perr. such transparent, glasslike secondary mouthspines are 

 found (De Loriol: Notes pour servir à l'étude des Echinoder- 

 mes. IX.), and in the family Odontasteridœ Verrill likewise one 

 or two mouthspines have that structure. 



These spines, in my opinion, are extremely interesting; I 

 cannot see but that they must be regarded as the H ото log a 

 of the sphaeridia of Echinids. These curious organs are 

 indeed only spines, which have been transformed into a homo- 

 genous, compact calcareous mass, the basal part alone retaining 

 traces of the original structure. Not seldom sphæridiæ may be 

 found, which have been so little transformed that one scarcely 

 knows what to call them: spines or sphæridiæ. An especially 

 striking example of this fact 1 have found in a specimen of 

 Echinus esculentus from the North Sea (a curious variety, resemb- 



