146 THE SPONGES OF THE WEST-CENTRAL PACIFIC 



toxas, 3 /x thick and 170 /x long. These are three times curved, as is typical 

 of toxas. 



The species micronesia is regarded as sharply characterized by its 

 typically shaped, but enormous, toxas. The species that was first described 

 as Clathria toximajor by Topsent, 1925, page 653, from the Mediterranean, 

 has toxas, 300 fx to 900 fx long, but these have a very peculiar shape, being 

 practically straight spicules with one little curve in the center. This curve 

 is of such a nature that each of the two long lateral projections is in line with 

 the other. The sponge described as Microciona mkrojoanna by de Lau- 

 benfels, 1930, page 27, from California, has typical toxas, some of which 

 were as large as 140 ju, ; but all of its spicules were enormous, the megascleres 

 being as large as 27 fx by 330 /a. 



The species originally described as Microciona dives by Topsent, 1891, 

 page 543, has anchorate chelas. The dermal spicules are diactinal tornotes. 

 This is obviously not a Microciona and therefore is transferred to the genus 

 Myxilla. 



The species described as Microciona bulboretorta by Carter, 1880, page 

 465, has no microscleres at all. It therefore is transferred to the genus 

 Epicles. 



The species described as Microciona longispiculum by Carter, 1876, 

 page 237, from deep water in the Atlantic Ocean, has no microscleres and 

 therefore is transferred to the genus Epicles. 



The species name is given in honor of Micronesia, which is the anthro- 

 pological term for that portion of the world which is discusssed in the present 

 treatise. 



Microciona placenta (Lamarck) de Laubenfels 



Text Figure No. 94 



This species is here represented by the following: 

 U.S.N.M. No. 22908, My No. M. 213, collected August 13, 1949, by diver 

 in the west part of the Truk lagoon, specifically at Lemotol Bay. The 

 depth was 4 meters, and the substrate was dead coral. 



This species is incrusting, 1 to 2 mm thick, and spreading laterally at 

 least 10 cm. 



The exterior and interior color in life was olive drab, and the con- 

 sistency was that of a colloidal jell. 



The surface is extremely smooth and lipostomous. 



The ectosome is not sharply separated from the endosome, the species 

 being so very thin. 



The skeleton consists of colloidal material and spicules which principally 

 are erect with bases next to the substratum and points outward. These are 

 smooth styles, varying towards being smooth subtylostyles. The size is 2 /x 



