POLYCLAD FLATWORMS — HYMAN 565 



Section Emprosthommata 

 Family Cestoplanidae . , 



Juvenile Cestoplanid 



Kemarks: There was present in the material from Ifaluk Atoll one 

 very juvenile cestoplanid, collected Oct. 1, 1953, from the reef ridge at the 

 north end of Falarik. A di-a\\ang was not made. It may be recalled 

 that a juvenile cestoplanid was previously reported from the same 

 general area (Hyman, 1955b), but in view of the immaturity of both 

 specimens a specific comparison is impossible. The specimen is de- 

 posited in the U. S. National Museum. 



Suborder Cotylea 



Family Pseudoceridae Lang, 1884 



Genus Pseudoceros Lang, 1884 



Remarks: The genus Pseudoceros is one of the largest polyclad 

 genera, comprising at present over 100 valid species. The genus is 

 easily recognized by the combination of smooth dorsal surface, ten- 

 tacles as upfolds of the anterior margin, and ruffled pharynx. The 

 species, however, are distinguishable mainly on shape and color 

 pattern and the one is distorted and the other often totally lost in 

 preserved specimens. Hence the identification of preserved specimens 

 usually offers formidable difficulty. Whether the male apparatus is 

 single or paired is a useful character and details of the male copulatory 

 apparatus may be of value in specific diagnoses. It now appears that 

 the shape of the pharynx may be decisive. In most species the pharynx 

 has a compact outline but several species are now known in which the 

 pharynx takes what I have termed the butterfly shape, putting out 

 lateral lobulations that increase in length in the anteroposterior di- 

 rection as in figure 10, c. 



In 1950 Marcus published a useful list of the described species of 

 the genus. In the thought of increasing the usefulness of this list I 

 here add some old species overlooked by Marcus and the species 

 described since that date: fulminatus (Stimpson) (1855), guttatomar- 

 ginatus (Stimpson) (1855), interrwptus (Stimpson) (1855), albicornis 

 (Stimpson) (1857), coccineus (Stimpson) (1857) , japonicus (Stimpson) 

 (1857), niger (Stimpson) (1857), affinis (Kelaart) (1858), atraviridis 

 (Kelaart) (1858), dulcis (Kelaart) (1858), fuscus (Kelaart) (1858), pur- 

 pureus (Kelaart) (1858), luteus (Plehn) (1897), izuensis Kato (1944), 

 nipponicus Kato (1944), evelinae Marcus (1950), mopsus Marcus 

 (1952), bajae Hyman (1953a), canadensis Hjmian (1953a), mexicanus 

 Hyman (1953a), montereyensis Hyman (1953a), coralliferus Hyman 

 (1954), micronesianus Hyman (1953b), and texanus Hyman (1955c). 



