PYCINASTER SENONENSIS. 95 



Genus— PYCINASTER, 1 nom. nov. 



Pycnaster, Sladen, 1891 (seep. 21), uou Pomel, 1883. Classif. method. Ecliin., p. 42. 



1. Pycinaster angustatus, Sladen sp. (see p. 21). PI. IX, figs, la, lb; PI. XXI, 



figs. 2, 2a ; PI. XXV, fig. 7 ; 

 PI. XXVI, figs. 4, 4 a, 4 6. 



This species appears to be quite common in the Upper Chalk. An exceedingly 

 well-preserved specimen is in the collection of Dr. Blackmore, of Salisbury. 



The following specimens, which belong to the genus Pycinaster, and probably to 

 this species, have been erroneously ascribed by me to other genera and species in 

 Part III of this volume (pp. 67-90). 



The single specimen described on p. 73 as a new species, Pentagonaster robustus, 

 is probably an immature form of this species. A collection of five ossicles described 

 (p. 89) as Pentaceros, sp., and the specimen figured on PL XXVI as Oalliderma 

 mosaicum, also belong to the species. The latter specimen should be described as 

 from the Upper Chalk. 



Dom Aurelien Valette has courteously enabled me to examine the syn-types of 

 his Arthraster senonensis (' Bull. Soc. Sci. Yonne,' 1902, p. 23). They prove to be 

 marginals of Pycinaster angustatus. Four ossicles referred by him to his Pentaceros 

 senonensis (vide infra) also belong to the present species. 



2. Pycinaster senonensis, Valette, sp. PL XXVI, figs. 1, la, lb; PL XXIX, 



figs. 6, 6 a. 



Pentaceros senonensis, Valette, 1902. Bull. Soc. Sci. Yonne, vol. lvi, pp. 17, 18, 



figs. 1, 2 (non 3—7). 

 — punctatus, Spencer, 1905. Autea, p. 88. 



Dr. Blackmore's material enables me definitely to ascribe this species to 

 Pycinaster, and to add the following new diagnosis and details : 



Specific Characters. — Body of large size. Breadth of marginalia more than 

 twice their thickness. All marginalia smooth or with very shallow hexagonal 

 spine-pits. 



Description. — The marginalia may be as much as 20 mm. high. They appear 



to be distinguished from the marginalia of P. angustatus, not only by their 



1 IIvkii/oj, compact, Homeric form of Kvuvot. Dom Aurelien Valette kindly pointed out the 

 prior use of Pycnaster to Dr. F. A. Bather, who suggests the above emendation. 



