HALOPSIS. 99 



development ; they are not capable of great expansion, and when short- 

 ened, the extremities are curled up. The ovaries, which are linear, 

 extend along the chymiferous tubes in such a way as to leave both the 

 actinal and abactinal extremities free (Fig. 142) ; the spherosome in- 

 creases very gradually in thickness from the circular tube towards the 

 abactinal pole. This species dijBers 

 from the >S'. lentlculare of the Falk- 

 land Islands, in having a smaller 

 free area, longer chymiferous tubes, 

 and more numerous tentacles ; it 

 grows from one and a half to two 

 inches in diameter, and half an inch 

 in height, is sluggish in its movements, is colorless, and has a gelatinous 

 disk of considerable consistency. These Medusae are frequently found 

 thrown up on the sandy beaches, encased in sand in such a way as to 

 be preserved from decomposition and loss of shape for several days. 

 This may explain the mode in which the few fossil Medusae known 

 have been formed. 



Massachusetts Bay, Nahant (L. Agassiz). 



HALOPSIS A. Agass. 



Halopsis A. Agass. ; in Proc. Bost. Soc. Nat. Hist., IX. p. 219. 1863. 



The genera Berenix and Carisochroma have been placed by Professor 

 Agassiz among the Williadae on account of their forking chymiferous 

 tubes. The discovery of Halopsis shows this association to Ijc un- 

 natural, and that most probably, when the genera Berenix and Cariso- 

 chroma are better known, they will be associated with Halopsis into a 

 distinct family, the Berinicidae of Eschscholtz. Whatever may be the 

 result, it is at least highly probable that their closer relations are with 

 the ^quoridae, and not with the Tubularian family of the WilliadjB. 



Halopsis OCellata A. Agass. 

 Halopsis ocellata A. Agass. ; in Proc. Bost. Soc. Nat. Hist., IX. p. 219. 1863. 



The genus Halopsis differs from the other iEquoridse by the presence 

 of large compound eyes, as in Tiaropsis, from three to six between 

 every two of the chymiferous tubes. There are likewise long tentacu- 

 lar cirri ; the flatness of the disk, the large number of tentacles, the 

 nature of the digestive cavity and of the genital organs, place this 

 genus among the ^quoridae. Two species are found on our coast. 



Fig. 142. The same as Fig. 141, seen in profile. 



