240 DISCOVERY REPORTS 



Diagnosis. Differing from Anasterias in a further reduction of the abactinal and 

 marginal skeleton, which in its poorest development consists of lateral transverse 

 tongues of plates (composed of two reduced marginals plus one to several abactinal 

 elements) abutting on the adambulacral plates; dorsal surface with much reduced, dis- 

 connected, scattered platelets, or a sketchy rudimentary reticulum (principally on disk) ; 

 or, especially in mature specimens, no plates ; integument thick, raised in mammillated 

 pustules which represent elaborated spine sheaths; adambulacral plates monacanthid; 

 no actinal spines, the actinal plates rudimentary, confined to disk, or present as an in- 

 conspicuous series crowded between the inferomarginals and adambulacrals ; gonads 

 open ventrally — paedophoric. 



Remarks. This is the Anasterias of most authors. It is closely related to true Anasterias 

 and differs chiefly in the development of the spine sheaths into glandular pustules 

 (probably pari pasii with the disappearance of spines and dorsal plates) and in the 

 disappearance of functional actinal plates. Various degrees of degeneration of the dorsal 

 and marginal skeleton are met with in the type species, perrieri. In some varieties the 

 abactinal skeleton is as well developed as in Anasterias ; in others it is practically absent. 

 There is direct evidence in specimens of perrieri from South Georgia that there is a 

 gradual degeneration of abactinal and marginal skeleton as the animal grows, as if the 

 calcium were required for the growth of the more important axial skeleton and essential 

 spines (i.e. the actinostomial ring, the ambulacral and adambulacral systems). In this 

 graded series the abactinal skeleton disappears with increasing age while the marginal 

 plates shrink in size, change their shape, and certain superomarginal connectives 

 disappear entirely. 



Verrill's genus Paedasterias was founded pretty largely upon an erroneous transla- 

 tion. Ludwig (1903, p. 42), in a synopsis of "Anasterias'', says: "Die Spagen haben 

 (mit Ausnahme der Armspitze) keinen oberen Randstachel; grosse Tatzenpedicellarien 

 vorhanden. . . .An. chirophora n.sp." Verrill diagnoses the genus:" . . .the upper marginal 

 plates being absent except as rudiments distally". But Ludwig in a major division of his 

 synopsis states that the upper marginal plates are present in chirophora. Koehler (1920, 

 p. 30) adopted Paedasterias, and added a new species, joffrei. As a matter of observation 

 it may be stated that there are reduced superomarginal plates in the species supposed to 

 lack them and that there is no valid generic hiatus between the forms with reduced 

 marginals and those having well-developed marginal plates and spines, such as adeliae 

 and perrieri. In fact the new species described below, L. hemiora, with greatly reduced 

 marginals, may turn out to be a variant oi perrieri, incredible as it now appears. 



Lysasterias is pretty much a genus of convenience. It appears to be an Antarctic off- 

 shoot of Anasterias which has suffered, along with Perknaster and some other genera, 

 a grave disturbance of calcium metabolism. 



