from the. North Pacific Ocean. 447 



plane of ramificatien of the colony. Aperture oval, com- 

 pressed, long but narrow, with two angles on the two sides, 

 and two very slightly developed teeth. 



Gonosome. Unknown. 



Locality. Port Ajan [M. Wosnessensky, 1848). 



Two little colonies of this hydroid were attached by the 

 hydrorhiza to the base of a colony of Selaginopsis pinnata. 

 The hydrocaulus is straight and gives origin on two sides to 

 branches alternately arranged and forming an acute angle 

 with the stem (PI. XVIL %. 17). The length of these 

 branches gradually diminishes towards the apex. The inter- 

 nodes of the principal stem, as also of the branches, are very 

 irregular; sometimes they are formed of a single pair of 

 hydrothec£e, sometimes of two or even three pairs. The 

 hydrothecffi (PI. XVIL figs. 18, 19) are greatly inflated in the 

 lower half, whilst the other half becomes suddenly very 

 strongly compressed, forming a neck. In the plane of rami- 

 fication (PL XVII. fig. 18) the colony has a very peculiar 

 aspect, in consequence of the inflated portion appearing to be 

 furnished with a very long and slender neck. This neck 

 usually makes a more or less acute angle with the principal 

 stem and the inferior half of the hydrotheca ; and this angle 

 sometimes becomes nearly a right angle (fig. 18, x ). On 

 turning the branch so that it may be seen from the side, the 

 liydrothecte assume a nearly cylindrical form (fig. 18 a) 

 slightly widened at the base, with the two teeth of the two 

 sides more or less developed. Sometimes the teeth are very 

 slightly developed, so that one would call them rather two 

 angles than two teeth. The aperture is compressed, as shown 

 in figs. 19 and 19 a. For the better understanding of the 

 form of the hydrothecse I have represented one of them 

 under a higher magnify ing-power and turned a little to one 

 sidL (PL XVII. fig. 19). 



Length of the colony 12 milliras. ; length of the hydrothecse 

 0'4, maximum breadth 0*2; width of the aperture 0*05; breadth 

 of the whole branch, including the hydrothecge, 0"7. 



This very curious form differs from all known species of 

 Sertularia by the compressed form of its hydrothecse. It is 

 represented in the collection of the Academy by two small 

 colonies attached to Selaginopsis pinnata, and probably verv 

 young considering their small size and the absence of gono- 

 somes. 



Sertularella Glarhii^ sp. n. (PL XVII. figs. 20-22.) 



Trophosome. Hydrorhiza forming a compact layer of hydro- 

 phytons. Hydrocaulus straight, long, cylindrical, not angu- 



