1889.] NATURAL SCIENCES OP PHILADELPHIA. Ill 



Hertwig. The correctness of Haddon's identification is quite as 

 doubtful as Hertwig's, if not a little more so. The form is certainly 

 a Sagartid and probably a Phellia, it being stated that it is very 

 similar to Hertwig's Phellia peetinata. 



Hertwig refers his Diplactis (Hormathia) delicatula to the family 

 Antheadce, on account of the diffuse endodermal nature of the 

 sphincter. The situation of the muscle and other characters make 

 it evident that Diplactis should be associated in the same family with 

 Oulactis. In the Phyllactidse as here limited we have several 

 grades of complication of the fronds. In Diplactis their structure is 

 exceedingly simple, being simply digitiform in D. bermudensis and 

 club-shaped in D. delicatula. In 0. fasciculata they are somewhat 

 more complicated, and from this the passage is easy to Verrill's 0. 

 (Lophactis) ornata, and from this to the very complicated structure 

 seen in 0. flosculifera. 



4. Diplactis bermudensis. n. Bp. (PI. VI. figs. 4 and 6, PI. VII, figs. 1 and 2.) 



A number of specimens of the form for which I propose this name 

 were obtained. The majority were in a partially contracted condi- 

 tion, but apparently the power of contraction is not fully developed 

 as in none were the tentacles completely concealed. The average 

 height of the specimens is about 1*5 cm. and the breadth nearly the 

 same, and thus D. bermudensis is decidedly smaller than D. delicatula. 

 The ectoderm has been almost entirely macerated away, so that the 

 external surface of the mesogloea is exposed to view. This presents 

 numerous transverse folds due to contraction, but in addition fine 

 linear depressed stride are present, both horizontal and longitudinal, 

 dividing the surface into numerous rows of small quadrangular ele- 

 vations visible to the unaided eye. The color throughout is a dirty- 

 green. 



The base is adherent, flat, and about the same size as the column. 

 It is marked by radiating and concentric stria?, continuations ot the 

 longitudinal and horizontal stria? respectively of the column. No 

 verruca? or tubercles occur on the column, though the quadrangular 

 areas produced by the stria? are slightly more prominent toward the 

 margin. This is well marked and smooth, and is separated from the 

 tentacles by a deep fosse (collar) near the bottom of which are about 

 12 short digitiform fronds about 1 mm. in height. (PI. VI, fig. 4p, 

 and PI. VII, fig. 1.) 



Between these fronds and the tentacles there is upon the endo- 

 dermal surface of the collar a sphincter (PI. VI, fig. 4, sp.) of the dif- 



