MOLLUSCS. 



299 



pilata. 



eac-li side. In Ilermwa the gills ;uc iiioie iiuiiierous, and tho tentacles, which are 

 broad and flattened, arc usually folded. Our New England species, //. cruciata, has 

 received its specific name from the cross-like marking of each gill. The 

 species of 3foiitagua, of which we have over half a dozen forms, and 

 the closely allied Eolis, have a large number of gills arranged in trans- 

 verse rows uj)on the sides of the back. They are very active animals 

 (for nudihranchs) and arc common on jnlcs of bridges, among the roots 

 of sea-weeds, and on rocky bottoms. They lay their eggs in gelatinous 

 spirals with wavy margins, resembling a lady's frill in general appear- 

 anc6. Fre(iuently bright colors are present, making these among the 

 most attractive of marine objects. 



In iJoto and allied forms the tentacles are retractile into cup-shaped 

 sheaths, while the branchiae are most curious bodies covered with minute 

 papilL-e. Uoto coronata, which extends from our shores to those of ^"^• 

 northern Europe, is a handsome object. It is scarcely more than half 

 an inch in length, but, small as it is, there is room for spots of orange, pink, yellow, 

 carmine, purple, and white. Possibly one of our most sti-iking forms is Dendronotus 



arborescens, with its 

 curiously Ijranching 

 gills, which, from 

 their thin, l)ushy ap- 

 pearance, \\a.\(i given 

 rise to both its gen- 

 eric and specific 

 names. This branch- 

 ing feature is also 

 seen in the tentacu- 

 lar sheaths which are 

 split up like the calyx 

 of a flower. The 

 general color is flesh- 

 red or brown. This 

 is one of the most 

 active of the naked 

 molluscs, and, when 

 confined in an aqua- 

 rium, is scarcely ever 

 <iuiet. It lies on 

 specially adapted for crcjejiing around upon them by 





'<^< 



^W -fkfc' 



?"?«? 



'^, 





.V 



4 



^7 



Fk;. ^'j. — Jjcndroitotus arhoresceus, bushy sea-slug. 



liydroids and sca-wceds, bein 

 its long and slender foot. 



The genus Scyllea, which has the body expanded into two long lobes, bearing the 

 gills on either side, is interesting from the fine instance of mimicry it affords. It lives 

 upon the gulf weed (S'irf/a.ssum) of the Atlantic and other seas, and with it is occa- 

 sionally drifted upon our shores. The large fields of this sea-weed which exist in the 

 tropical Atlantic have a fauna of its own, and among other foi-ms are numbers of fishes, 

 craV)s, shrimps, and the slugs now under discussion. Were it not for its protective 

 resemblance to the sea-weed on which it dwells, a resemblance embracing both form 

 and color, Scyllea pelagicd would furnish many a fine mouthful for its voracious asso- 

 ciates, and the species would soon become extinct. 



