36 Ths Microscope, 



The oral aperture is obliquely i^laced (Plate II, fig. 21), the 

 oral annulus being strongly beaded. 



The oeso})hagus is foom one-third to one-fourth the length of the- 

 body, the margins of the cavity being minutely and irregularly 

 crenulated. In the mature adult there are often developed cons})ic- 

 uous, temporary, lateral diverticula, or passages of unequal length, 

 (Plate II, fig. 19), which seem to extend from the central into the 

 lateral passages. They are opened and closed at the animal's will, 

 but whether by irregular muscular action, or whether they are nor- 

 mal pai-ts of the organ, I do not know. 



A variety is rarely met with which differs from the above form 

 in its smaller body, the fewer and much larger scales, and in the 

 presence of two, long, recurved spines developed on each lateral 

 margin near the posterior extremity. I have obser\'ed but a single 

 individual of this variety. 



The egg is j^ inch long. One surface and both ends are 

 armed by hollow papillfe, or short, hollow spines, the summits of 

 both papillae and spines being bifid or emarginate, as in Plate II, 

 tig. 20. The long and short appendages are often present on the 

 same specimen. 



8. Choitonotus rhomboides, sp. nov. — Plate 11, tigs. 31-35. 



The characteristics of this previously undescribed species are the 

 unusual form of the head, the small rhombic scales, and the extremely 

 long caudal appendages. The body itself is long and narrow, meas- 

 lu-ing about -^^ inch in length. The posterior extremity is divided 

 into two furcations or branches, each between one-third and one- 

 fourth the length of the entire animal. These taper gradually to- 

 their free ends, and are composed of about twenty slightly con- 

 stricted rings or joints. They are freely movable and flexible, and 

 form tail -like organs, unique so far as this genus of microscopic 

 animals is concerned. At their junction with the posterior extremity 

 of the body they are separated by a more or less conspicuous emar- 

 gination, as shown in Plate II, fig. 31, where but one of the caudal 

 appendages is delineated. They invariably appear, so far as I have 

 examined different individuals, to be quite hollow and empty. I 

 have been unable to see the duct of the caudal glands ; and the 

 muscular apparatus of the part is invisible. 



The broad head is formed of three lobes, a frontal and two 

 lateral. The former terminates on each side in a single, acuminate, 

 hook-like process, habitually in close api:)Osition with the anterior 

 lateral region of the lateral lobes, of which the posterior extremities 



