208 



CTENOPHORiE. 



Part II. 



of Europe ; the second, -whicli I have named Pkurohmchla rhododadi/la, occurs on the 

 eastern shores of the northern United States; and the third was recently observed 

 on the north-west coast of America hy my son, Alexander Agassiz. 



Though, at first sight, our Pleuroln-achia appears spherical, it is slightly com- 

 pressed in a direction at right angles with the base of the tentacles; so that the 

 coeliac diameter is really shorter than the diacadiac. As it is of great importance 



tVom tlic range of dift'crences observed among indi- 

 viduals of diftercnt, ages of the species I liave 

 described as PI. rhododactyla, I hold that the two 

 species described by Forbes and Patterson are one 

 and the same with PI. Pileus, the rows of loco- 

 motive flappers being comparatively broader, and 

 the number of flappers less, in young than in old 

 specimens, and the tentacles, having generally not 

 yet sustained any injuries, are longer and more 

 active. I therefore consider Cydippe Flemingii 

 Fori., Cydippe pomiformis Patters., Beroe ovatus 

 Flem., and even Cydippe Infundibulum Esch. (Beroe 

 Miilleri Less.), as synonymes of Pleurobracliia or Cy- 

 dippe Pileus. Whether the Mediterranean repre- 

 sentative of this genus, described as Cydippe densa 

 Esch., to which Beroe Pileus Risso and Beroe 

 albens Forsh. also belong, is identical with tlie 

 northern PI. Pileus, or not, I have no means of 

 ascertaining ; the red tentacles seem to indicate a 

 specific diflerenee, and the circumstance that this 

 species has thus far only been noticed in tlie 

 Lusitainc fauna, while PI. Pileus belongs to (he 

 Celtic fauna, would justify this inference. The 

 Beroe Pileus of Fabricius (which must not be con- 

 founded with Cydippe Cucullus, as was done by Eseh- 

 scholtz) is very likely the North American PI. rho- 

 dodactyla. This Beroe Cucullus, erroneously called 

 Cydijiiic Cucumis by Lesson, is a Mertensia. identical 

 with the Beroe Pileus of Scoresby (Merlensia Scores- 

 by Less.), and also identical with Beroe ovum Fahr. 

 (Cydippe ovum Esch.). Lesson has made another 

 mistake in referring Cydij)pe bicolor Sars to his 

 Cydippe Cucumis. Sars's species is a genuine 

 Pleurobracliia, distinct from PI. Pileus, but closely 

 allied to our PI. rhododactyla. It is, in fact, the 

 European representative of the PI. rhododactyla, 

 and, like this, belongs to the boreal fauna ; while 



Mertensia Seoresbyi, which should be called M. 

 Cucullus, is an arctic species. PL Bachei, dis- 

 covered by my son on tlie shores of Washington 

 Territory, is another species with red tentacles, but 

 difters from PI. rhododactyla in having a longer 

 funnel, a sliorter cteliac cavity, and the actinal part 

 of the tentacidar sac also sliorter. PI. bicolor, 

 judging from Sars's description, h.as white lateral 

 threads, the tentacle itself being alone red. To these 

 species must be added Beroe Basteri Less, from 

 the coast of Peru, Beroe rosens Q. and G. from 

 the straits of Timor, and Beroe Santonum Less., 

 which is prol)aIdy identical with PI. Pileus. Les- 

 son refers tiiese three species to the true Beroids, 

 but they unciuestionably belong to the genus Pleuro- 

 bracliia : tlie tentacles must have been overlooked. 

 No true Beroid ever has the form of these Aca- 

 leplis. The genus Janira, which comes nearest to 

 Pleurobracliia, embraces, as far as I know, only 

 the following three species : Cy'^'l'l"' elliptica Esch., 

 Beroe Cucumis Mert., and Beroe (dongatus Q. and 

 G. Janira hexagona is a Callianira, and Janira 

 octoptcra a Blartensia, well to distinguish from 

 Mertensia, though both belong to the family Mer- 

 tensida\ To Eschscholtzia I refer only Cydippe 

 dimidiata Esch. ; Eschscholtzia glandiformis Less, is 

 the type of (he genus Dryodora (Mertensia Gegenb.) ; 

 wliile Eschscholtzia cordata is the type of the genus 

 Gegenbauria Ar/., and belongs to the family of 

 Mertensida'. Cydippe liormiphora is also the type 

 of a distinct genus, for which I would propose the 

 name liormiphora : it is closely allied to Esch- 

 scholtzia and Pleurobraehia, and belongs with them 

 to the family of Cydippidre proper. Cydippe brevi- 

 eostata Will, ami Cydippe quadricostata Sars are 

 very likely young Ctenophoiw Lobata^ according 

 to the observations of McCrady. 



