74 PROCEEDINGS OF THE NATIONAL MUSEUM vol. los 



is small, somewhat slender, and is housed in a part of the male antrum 

 (penis pocket) separated from the general male antrum by a penis 

 sheath, a circular fold with rather thin margins projecting into the 

 male antrum. Distal to the penis sheath the male antrum proceeds 

 as a somewhat elongated tube to the male gonopore. 



The female gonopore occurs not far behind the male pore and leads 

 into a tubular vagina invested with a layer of circular fibers. The 

 vagina proceeds dorsally, widening considerably, then curves back- 

 ward, receiving the common oviduct at the curve. It then continues 

 posteriorly and downwards as a vaginal duct. This duct makes a 

 loop and proceeds, widening somewhat, to the vaginal pore in the 

 midventral wall, somewhat farther behind the female gonopore than 

 the latter is from the male gonopore. The vaginal duct is heavUy 

 muscularized with circular fibers. 



DiFFERNTiAL DIAGNOSIS: Ommatoplana oceaniea differs from other 

 known species of the genus in the presence of tentacles and in the 

 black color of the tubercles. 



Holotype: One whole mount deposited in the U. S. National Mu- 

 seum (No. 25941); also, one set of sagittal sections of the copulatory 

 region. 



Remarks: If I am correct in assigning this species to Ommatoplana, 

 then Ommatoplana is a stylochid, not a cryptocelid as supposed by 

 Bock (1913). Certainly, because of the loss of important sections, 

 the original description of Ommatoplana does not furnish the neces- 

 sary information to decide to what family of the Craspedommata it 

 belongs. It is further evident that Mexistylochus Hyman, 1953, is a 

 synonym of Ommatoplana. As the combination Ommatoplana 

 tuherculata already exists, it becomes necessary to suggest a new 

 specific name for my species Mexistylochus tuberculatus, and I propose 

 mexicana. The genus Ommatoplana then comprises at present the 

 species tuherculata Laidlaw, 1903, mexicana, new name, levis (Hyman, 

 1953) and the present oceaniea. The last three species are very 

 similar as to eye arrangement but, according to Laidlaw's figure, 

 tuherculata differs decidedly in this respect. The peculiar disposition 

 of the cerebro frontal eyes in this figure, without bilateral arrangement 

 or cerebral or tentacular clusters, suggests some abnormality or injury 

 in the specimen in question. 0. levis differs from the other three 

 species in lacking the characteristic dorsal tubercles. The great 

 similarity of the copulatory apparatus in the three species in which it 

 is fully known is very surprising. Anastomosis of the intestinal 

 branches into a fine-meshed network appears characteristic of the 

 genus, Ommatoplana is very close to Cryptopliallus but differs from 

 it in the well developed, though small, prostatic vesicle and in the 

 separate opening of the vaginal duct. 



