Helminth Fauna of the Dry Tortugas. i 77 



4. Littianus griseus. 



July 5. One small larva from this host, while much smaller than usual 

 for this species, agrees so closely with it in the arrangement of the hooks 

 that it also is recorded here. 



Another like it was collected on July 10. 



Dimensions of living specimen, slightly compressed, in millimeters: 

 Length 3.64; head, length 0.49, breadth 0.63; neck, length 1.96, breadth, 

 anterior, 0.35; bulbs, length 0.51, breadth 0.14; proboscis, length, estimated, 

 1.40, diameter, exclusive of hooks, 0.04; length of largest hooks, about 0.021. 



18. Rhynchobothrium simile sp. nov. 

 (Plate 5, figs. 30-37, and plate 6, fig. 38.) 



This tetrarhynch belongs to the group of comparatively large forms, 

 represented by R. imparispinc and R. speciosum, to which it bears a close 

 resemblance. It resembles the latter in the general habit of the scolex and 

 neck, but is more like the former in the character of the hooks. Indeed, 

 at the time of collecting it was thought to belong to that species, and it was 

 not until the hooks were examined critically that the great difference be- 

 tween them and those of R. iinparispine was revealed. The general charac- 

 ter and arrangement of the hooks may be seen in the figures. 



Bothria, in alcoholic specimens, about as broad as long, emarginate on 

 the posterior border, with margins raised so as to make the face a deep 

 cup; in marginal view distinct from each other, the posterior ends flaring 

 slightly. Head in both marginal and lateral views wider than neck. The 

 bothria are attached on those sides of the head which correspond to the flat 

 surfaces of the strobile. Contractile bulbs rather long and slender, the 

 retractor muscle of the proboscides being attached at the posterior ends of 

 the bulbs. 



The first segments begin near the base of the neck, at first as faint trans- 

 verse lines, then as distinct segments much broader than long, lengthening 

 posteriorly, soon becoming squarish, and ultimately longer than broad. 

 The entire strobile is linear and the segments squarish. In a typical speci- 

 men, measuring 50 mm. in length, the last segment was 2 mm. in length 

 and 1.5 mm. in breadth. The average length of the last four segments was 

 a little less than 2 mm. 



The genital cloaca is at about the posterior third, and is a shallow notch 

 with abrupt sides. In glycerin the segments show longitudinal striae like 

 those noted in R. imparispine (Report U. S. Fish Com. for 1887, pp. 840- 

 843, plate xn, figs. 6-9). 



The proboscides are long and beset with hooks of many different pat- 

 terns, the longest of which measures as much as 0.2 mm. 



Dimensions of a specimen mounted in balsam, in millimeters : Length 

 of head and neck 6; bothria, length 1.20, breadth i.oo; bulbs, length 2.5, 



