CHARACTERISTIC DEEP-SEA TYPES. — ACALEPHS. 133 
not more than five genera were known from the Western At- 
lantie, while at the present time that number is more than 
doubled. 
Of the aberrant group of Rhizophyside no less than three 
species are now known from the Gulf Stream. One of the most 
y wu 
Fig. 427. — Atolla Bairdii. 2. (Fewkes.) 
characteristic species of the group, Pterophysa, has been men- 
tioned in the chapter on the Pelagie Fauna. 
Agalma Okenii (Fig. 428) is common in the Gulf Stream ; 
it is easily recognized by the rigid nature of the colony, and 
by this can at once be distinguished from the Agalma found 
at Newport. The end of the axis opposite the float bears thick 
covering scales, while in the Newport Agalma the scale 1s leaf- 
like, and not eubieal or polygonal. 
One of the least known genera of Physophor is the genus 
Athorybia. It is remarkable in many ways, and differs from all 
known physophores in the character of its covering seales and 
