GEMMARIA. 289 



This elegant little hydroid was found by Mr. Hincks inhabiting a deserted bivalve shell in 

 Salconibc Bay, on the soutli coast of Devonshire. He informs us that the hydranths do not 

 appear to measure more than one sixth of an incli in height. Tlie verticillate tentacles are stout, 

 and with their capitula large ; the seattered tentacles are very slender, with small capitula ; 

 and decrease very markedly in size towards the base of the hydranth. The hydranths when 

 fully extended become very slender. Hincks could not satisfy himself that a hydrocaulus was 

 here present even in the rudimental condition of this part in Clava. It is probable, however, that 

 its very imperfect development caused it to be overlooked. 



GEMMARIA, WCradij. 



Name. — Yxom. gemma, a gem ; so named from the sacs of gem-like thread-cells in the 

 walls of the umbrella. 



Zanclea, — M'Crady, Gyrauophth. 

 Gemmaria (provisionally), — M'Crady, id. 



TROPHOSOME. — Htdrocaulus developed, invested by a perisarc, and rooted by 

 a creeping filiform utdroriiiza. Hydranths claviform, with scattered capitate 

 tentacles. 



GONOSOME. — Planoblasts developed from the body of the hydranth. Um- 

 brella at time of liberation deep bell-shaped ; manubrium moderately developed, 

 destitute of oral tentacles or lobes ; marginal tentacles two, developed from the distal 

 extremities of two opposite radiating canals, the alternate canals having each a small 

 tentacular tubercle at the corresponding point ; the tentacles commence each wnth a 

 large bulbous dilatation destitute of distinct ocellus, and are for the remainder of their 

 course set with pedunculated sacs filled with thread-cells ; from the base of each tentacle 

 and intermediate tubercle, a ccecal claviform tube, fiUed with thread-cells, extends for 

 some distance in the walls of the umbrella, parallel to the corresponding radiating 

 canal. 



M'Crady captured in the open sea at Charleston, South Carolina, a medusa which he 

 regarded as an immature specimen of a form referable to the genus Zanclea of Gegenbaur. Having 

 some doubts, however, as to the correctness of this determination, he suggested the name of 

 Gemmaria as a provisional designation to be used in the event of more conclusive observations 

 failing to justify the allocation of the medusa in the genus Zanclea} 



^ M'Crady, ' Gymnoplithalmata of Charleston Harbour.' 



