POLYCLAD FLATWORMS — HYMAN 553 



CopuLATORY apparatus: This is shown in sagittal view in figure 

 3a. The two gonopores are very close together. The male apparatus 

 contains an excessively long penis stylet, represented as solid in the 

 figure, although actually hollow. From the male gonopore the male 

 antrum ascends dorsally as a tubular canal, widens slightly to accom- 

 modate a penis sheath, then curves slightly backward, continuing to 

 ascend, and then turns anteriorly as a long narrow canal with a thick 

 muscular investment. Anteriorly it gi-adually widens, then cm-ves 

 ventrally to a slightly mdened chamber that houses the small penis 

 papilla from which the very long stylet springs. The stylet occupies 

 the whole of the very long male antrum and even protrudes from the 

 gonopore. Extending posteriorly from the penis papilla in a hori- 

 zontal plane is seen the oval prostatic vesicle into which the ejacula- 

 tory duct projects as diagnostic of the genus Notoplana. Proximally 

 the prostatic vesicle is entered by a small oval seminal vesicle with 

 the usual muscular wall. 



The female apparatus is also long and tubular. The short tubular 

 female antrum ascends from the female gonopore, then widens to a 

 vagina that slants dorsally and posteriorly. It is lined by a cuboidal 

 epithelium and has a good muscular investment. After receiving from 

 below the common oviduct, the vagina continues unaltered as a long 

 duct of Lang's vesicle that makes an S turn, then proceeds posteriorly 

 to enter the oval, thin-walled Lang's vesicle of moderate size. 



Differential diagnosis: Of the many species of Notoplana few 

 are provided with a long penis stylet. The stylet of the present 

 species seems to exceed that of all others in relative length. The eye 

 arrangement and proximity of the gonopores also differentiate Noto- 

 plana micronesiana from other long-stjdetted species of the genus. 



Holotype: USNM 28643, anterior part as whole mount, copulatory 

 region as sagittal serial sections (one slide). 



Euplana gigos (Schmarda, 1859) 



Remarks: This is one of the most common and widely spread of 

 Indo-West Pacific polyclads and is easily recognized by the charac- 

 teristic color pattern, which has been excellently figured in color by 

 Laidlaw (1902) and Kato (1934). This species was previously dis- 

 cussed (Hyman, 1955b), and hence comment here will be limited to 

 distributional records. Four specimens (USNM 28644) were collected 

 by D. H. Johnson on Oca Point, Guam, June 26, 1945. The largest 

 of these was 90 mm. long, preserved, with the gonopores 15 mm. apart. 

 Five specimens (USNM 28645-USNM 28647) were collected by Cadet 

 Hand, July 2, 31, and Aug. 2, 1954, at Kapingamarangi Atoll, at the 

 southern border of the Caroline Islands. These are new records for 

 the species but there is little doubt that this polyclad is spread through- 



