[17] MEDUSJ3 FROM THE GULF STREAM. 943 



same way as the exumbrella, by a deeply incised coronal furrow, into two 

 separate principal arete, which are connected only by the thin gelati- 

 nous ring at the bottom of the coronal furrow." In most of my speci- 

 mens of Verrillii I was able to discover this furrow on the subum- 

 brella, but in none was it so deeply incised as in Wyvillii. The coro- 

 nal ditch can be seen on the oval side of the umbrella, and can be 

 used as a line of division between a central subumbral disk and a sub- 

 umbral corona. The latter region is formed by two zones, an external per- 

 ipheral opaque muscle {onus. cor. e), and an inner, thin, translucent, {mus. 

 cor. i). In most of its specimens there are no deep radial furrows on the 

 subumbral surface of the corona, and the lower surface of the corona is 

 smooth. Through the translucent inner muscle of the corona on the 

 subumbral side can be seen the triangular bases of attachment of the two 

 muscles to each tentacle already described, alternating with radial gelati- 

 nous clasps {cl.)j by which the circular muscular system or the lower floor 

 of the subumbrella is bound to the lower surface of the umbrella. These 

 pairs of clasps {cl.) lie in the same radii as the sense-bodies, and equal 

 them in number in different specimens. 



From the subumbral wall of the central disk hang some of the most 

 important organs of the digestive and generative system. The wall 

 itself is fastened to the lower surface of the umbrella by four gelatinous 

 pillars, which are so broad that small orifices only remain between 

 them. The space left between the subumbral wall and tbe lower sur- 

 face of the umbrella is the stomach, opening by these four orifices into 

 a coronal sinus. The walls of the subumbrella, or lower flooi' of the 

 disk, are muscular, in which is a layer of circular fibres, and on tbe 

 lower surface eight well-developed deltoid muscles passing over or 

 bridging the space between the central disk and corona, tbus helping 

 to form the membrane-like body at the fundus of the coronal ditch. 

 These deltoid muscles are 45<^ apart, separating the outer appendages 

 of the central disk in the following manner: 



The most peripheral set of appendages to the wall of the subum- 

 brella is a ring of oblong, bean-shaped bodies (oa.), eight in number. 

 Tliese bodies are the ovaries, and they are found on the outer rim of 

 the subumbral portion of the central disk. The four alternate radial 

 deltoid muscles just mentioned separate these eight glands into four 

 pairs, of which, consequently, there is a single pair in each quadrant. 

 An inequality in the distances between adjacent sexual glands is one of 

 the prime differences between the two genera AtoUa and Collaspis. 



The whole of the middle region of the subumbral surface of the cen- 

 tral disk is occupied by the walls of the proboscis. In the largest 

 specimens this portion is wholly destroyed, and only one or two of the 

 sexual glands remained, while in the smaller I was able to investigate 

 the main peculiarities of this structuie. 



The general shape of the proboscis of Atolla recalls that of the genus 

 Jjinerges, and h^s more lil^enesses to that of the Ephyridi3e than the cur- 



