ART. 12 HEXACTINELLID SPONGES — OKADA 21 



HYALONEMA (CYLICONEMA) APERTUM SOLIDUM, new subspecies 



Plate 1, Figures 1, 2 



In the collection are three specimens representing a new form*. 

 They were found at three stations not far apart. 



Table 8. — Measurements of 3 specimens of Hyalonema (Cyliconema) apertuin 



solidum 



Specimens A (holotype, U.S.N.M. No. 22054) and B are tulip- 

 shaped and have a deeply concave gastral cavity, the surface of 

 which is perforated with few excurrent apertures ; while specimen C 

 shows an entirely different outer configuration, forming a shallow 

 transversely expanded body like the fruit of a lotus. The gastral 

 surface is nearly flat, showing the irregular lozenge form with a thin- 

 edged outer margin. 



The difference between the external appearances of these specimens 

 originally induced me to contemplate the establishment of two dis- 

 tinct species, but microscopic observation shows agreement in their 

 spiculation to such an extent that I have decided to consider all one 

 form. 



One of the chief characters separating II. {Cyliconema) afertum 

 sollduiii from apertum proper is to be found in the shape of the ma- 

 crami^hidisk, which presents a constant form as follows: The ter- 

 minal disk of this amphidisk is somewhat semicircular, contracting 

 inward on either side at the base, and curved inward at the ends, with 

 the proportion of the breadth and the height in the marginal teeth 

 nearly always 1 : 1.5. 



