6o BULLETIN OF THE LABORATORIES 



margin of the shell seems to be granulated and extends beyond the 

 body-cavity. The tail often is directed at right angles to the body and 

 is then overlooked. The lorica is about .20 mm. in longest diameter. 

 The tail measures over .07 mm. The trochal disc, when expanded, 

 is .05 mm. wide. A small specimen, but fully adult was but. 17 mm. 

 long. Mr. Stokes mentions a species of this genus but does not iden- 

 tify it. There are two other species, viz, P. elliptica and P. clypeata, 

 Ehr. , which latter occurs as a parasite on species of Assellus. I have 

 a confused recollection of having seen such a rotifer parasitic upon 

 Gammarus. Pteivdina complanata of Gosse is almost certainly identical 

 \\-ith Pt. patina. 



FAMILY ASPLANCHN.EA. 



This family includes abberant rotifers, which lack the posterior 

 opening of the digestive organs and are considerably reduced in other 

 respects. The foot is sometimes almost entirely absent, its position 

 bjing marked in these cases by the glands simply. The body is sac- 

 like and often consists of a single segment in which the various inter- 

 nal organs are very readily seen. The head is broad and sparsely 

 ciliated. The maxtax is enlarged and to it is appended an extensible 

 crop, while the incus is not highly indurated and the mallei are modi- 

 fied to form a prehensile pair of nippers or pliers. The stomach may 

 be very extensible and a part is very highly glandular. The water- 

 vascular system is highly developed and there is generally an accessory 

 canal bearing the minute beaker cells, while the lateral vessels them- 

 selves are tortuous and elaborate. Most of the species are carnivor- 

 ous, while others live upon alg?e and like i)Lants. 



GENUS ASPLANCHN.EA, Gosse. 



The genus is characterized by the sac-like body and the large size 

 and well differentiated organism as compared with AscomorpJia. The 

 details mentioned under the family apply. 



ASPLANCHNA MAGNIFICUS Sp. 11. 



{Plate II, Fig. 2.) 



This, the largest species of the genus, is most like A.^Myrmeleo.^ but 

 is considerably larger and appears to differ from it in several other par- 

 ticulars. The general form is a prolate spheroid truncated anteriorly 

 and slightly flattened ventrally. The oral end is furnished with six 



