30 bulletin: museum of comparative zoology. 



DINEMA, Van Beneden, P. J., 1867. 

 Dinema jeffersoni,^ nov. sp. 



rig. 126, Plate 37. 



Specific Characters. — The bell is dome-shaped and higher than it is broad ; 

 the hei'^ht beiny about 1 mm. and the breadth 0.75 mm. The outer surface 

 is sparsely sprinkled with nematocyst cells. There are 2 short marginal ten- 

 tacles and 2 well-developed tentacle bulbs. The tentacles are covered with 

 numerous small, wart-like, nematocyst-bearing swellings. The basal bulbs 

 are well developed. There are 4 ocelli, one in each tentacle bulb. These 

 ocelli are ectodermal and are situated on the centripetal sides of the bulbs. 

 The velum is well developed. There are 4 straight narrow radial canals and 

 a simple slender circular vessel. The proboscis is about as long as the height 

 of the bell cavity. It is simple, round, and tubular, and the mouth-opening 

 is situated at the extremity of a short cylindrical neck. A simple, short- 

 style canal extends upward from the gastric cavity into the gelatinous sub- 

 stance of the bell. The entoderm of the tentacles and tentacle bulbs is of a 

 delicate green. The ocelli are bright red-brown, and the entoderm of the 

 proboscis is flesh-colored. This form is occasionally met with at the Tortugas 

 late in May and early in June. 



Dinema floridana, nov. sp. 



Specific Characters. — The bell is about 4 mm. in height and 3 mm. in 

 diameter. The gelatinous substance is thin and uniform, and the side walls 

 of the bell are vertical. There are 2 well-developed, radially situated tenta- 

 cles. Near the distal end of each of these tentacles there is a large knob- 

 shaped swelling which terminates in a thin, nematocyst-bearing lash. The 

 knob-shaped swelling is hoUow and is connected with the general gastro-vas- 

 cular system of the medusa by means of a narrow tube which extends through- 

 out the length of the entodermal core of the tentacle. The basal bulbs are 

 not large and there are no ocelli. In addition to the 2 long tentacles there 

 are 2 simple rudimentary tentacle bulbs 90° from the well-developed tentacles. 

 The velum is well developed. There are 4 straight narrow radial canals. 

 The proboscis is flask-shaped, being narrower at its base than at the middle of 

 its length. It extends a short distance beyond the velar opening, and the 

 mouth is a simple round opening, at the extremity of a long narrow neck. 

 The entoderm of the proboscis and tentacle bulbs is bright yellow. The en- 

 toderm of the swollen distal ends of the tentacles is yellow flecked with 

 orange. 



A single specimen of this medusa was found at the Tortugas, Florida, 



June 17, 1897. 



1 Named after Fort Jefferson, at the Tortugas, Florida. 



