Narrative ov Bahama Expedijion. 223 



But a single sea-urchin was secured liere, an Aspidudiadcma, 

 which does not agree very well with either species described 

 by Agassiz. The spines are ver}' long and banded regularly 

 with purple and white. The characteristic sheathed pedicel- 

 lariat are w^ell shown, but differ somewhat from those pre- 

 viouslv described. So far as I can ascertain, this genus has 

 not hitherto been found at a less depth than ninety-live 

 fathoms. 



The comparali\'e meagreness of the collections so far as the 

 higher forms are concerned, was more than atoned for b}' the 

 marvelous series of hydroids from the ridge connecting the 

 two islands. No less than twenty-six species were brought up 

 in the ten hauls of the tangles, of which eighteen are appar- 

 ently new. It will thus be seen that this spot is one of 

 perhaps unprecedented richness in its hydroid fauna. In less 

 than a single day's dredging here, we brought up a greater 

 nuniber of species of this interesting group than rewarded our 

 week's work off Havana, where we secured twenty-one 

 species in sixteen hauls, or on the Pourtales Plateau, where we 

 secured twenty-three species in forty-three hauls. The pro- 

 portion of new species was also far in excess of anything found 

 elsewhere. 



The familv Haleciu.*: was represented by llalcciiini inac- 

 roccplialiiiii Allman, characterized b}' very large hydranths 

 and small h3'drothecaj, and a new species of Ilalecium which is 

 very minute, and was found on a bit of sea-weed completely 

 buried in a growth of alga and other matter adherent to the 

 sea-weed. It had the curious habit of growth b\- which new 

 hydrophores sprouted from the old ones just below their 

 mar(j;ins. The common Ohclia inarQ-inata Allman was found 

 here, and a species of campanularian, for which a new genus 

 ma}' be necessary unless it can be accommodated in the genus 

 CalyccIIa of Hincks. Three species of HcbcUa. all apparently 

 new', complete the list of campanularians. 



Among the Sertuearid--e are two new species of Scrtiilaria, 

 one of which resembles the next genus in the fact that the 

 livdrotheca' are in pairs and contingent, although they are 



