136 MCMURRICH. [Vol. V. 



with its longitudinal muscle on the ventral face, forming a pair 

 consequently with the imperfect mesentery just described. All 

 the perfect mesenteries, including the directives, possess mesen- 

 terial filaments and reproductive organs. Dorsal to the mes- 

 entery last mentioned is a pair of imperfect mesenteries (VIII), 

 followed by a pair consisting of a ventral imperfect (VI) and a 

 dorsal perfect mesentery (II), and dorsal to this pair is a second 

 pair of imperfect mesenteries (VII), and then come the dorsal 

 directives. The figure given is somewhat diagrammatic, since 

 the longitudinal muscles of the imperfect mesenteries are only 

 distinct in their uppermost part, while those of the perfect 

 mesenteries are more clearly marked out lower down. 



On the supposition that the paired mesenteries develop suc- 

 cessively, this form represents a stage succeeding Gonactinia, 

 from which it differs only in the development of the second pair 

 of paired mesenteries. 



Another arrangement occurs in Peachia, whose internal struc- 

 ture has been described by Haddon ('89) and Faurot ('90). In- 

 stead of referring to the accounts of these observers, however, 

 I shall take the opportunity of describing the structure of a 

 form which agrees closely with Peachia, and which occurs upon 

 our Eastern Coast, being found at Nantucket and the neighbor- 

 ing coasts, in Long Island Sound, and probably as far south as 

 Charleston, South Carolina. 



I refer to the form originally described by L. Agassiz ('59) as 

 Corynactis albida, but referred by Verrill ('64) to the genus Hal- 

 campa. Previous to Agassiz' description, however, Stimpson ('56) 

 had described under the name of Actinia prodncta a form from 

 the coast of South Carolina. Verrill also assigned this to the 

 genus Halcatnpa, considering it distinct from the more northern 

 H. albida, but later united the two forms under the name Halo- 

 campa {sic) prodncta. This union seems to be perfectly justifi- 

 able, there being apparently no well-marked characters upon 

 which to base a separation. 



Halcampa prodncta has been figured and described, so far as 

 its external characteristics are concerned, by Verrill ('64), so 

 that I shall confine my attention here solely to some points 

 in the internal anatomy. The stomatodreum is comparatively 

 short, and is marked by longitudinal ridges corresponding in 

 number with the mesenteries. A single siphonoglyphe, marking 



