Fam. 3, Plate 2. 



Genus 11. DENDRONOTUS,* Alder and Hancock. 



Corpus elongatum, lateribus compressis, ssepissime lato altus : pallio imllo. Caput subinferius, 

 velo parvo, ramoso, obtectum : maxillis corneis. Tentacula duo dorsalia, clavata et laminata, intra 

 vaginas retractilia. Bronchia cylindrical ramosse, linea Ulrica utrinque dorsi dispositai. Pes linearis, 

 gracilis. Orificia generationis et ani ad latus dextrum. 



We have found it necessary to institute this genus for the well known Tritonia 

 arborescens of authors and its allies, which are distinguished from the true Tritonia 

 {T. Hombergii, &c.) by the form of their tentacles, the want of a sub-pallial ridge on the 

 sides of the back, and the free arborescent nature of their branchiae. These characters 

 alone had induced us to consider them generically distinct before we had an opportunity of 

 examining their internal structure ; but it was not until we had dissected each that we were 

 aware of the full extent of their differences ; the gastric system of Dendrorwtus presenting 

 the ramifications so peculiar to the family TJolididce, while the stomach of Tritonia consists 

 only of a simple pouch without appendages, as in the Doridida ; the liver in the former 

 instance being much broken up and occupying the sides of the ramifications, whilst in the 

 latter it forms a single mass in the posterior part of the body. This important character 

 obliges us not only to form of the species so differing a new genus, but to remove them into 

 the family Eolidida, to which, from their structure, they properly belong. Even in an 

 anatomical point of view, however, the genus Bendronotus will be found to have only 

 partially assumed the characters of this family, retaining still much resemblance to the 

 Tritoniadce, and constituting one of those transition forms so often found uniting the 

 different types of organization in the animal kingdom. 



The body is elongated, much compressed at the sides, and tapering to a point behind. 

 The back is rounded, and has no vestige of a carinated ridge at the sides, or rudimentary 

 cloak, as is observable in Tritonia. The veil is short and more or less branched, covering 

 the head, which is sub-inferior and indistinct. There are two tentacles, which are dorsal, 

 clavate, and transversely laminated on the upper part as in Doris: they are retractile 

 within sheaths, generally branched at the margins. The branchiae are arranged in a single 

 line on each side of the back, rising gradually from it at their base, and dividing into 

 cylindrical branches much resembling a tree without leaves, or, perhaps more closely, a 

 branch of coral. This structure is different from that of Tritonia, whose branchiae are com- 

 posed of flattened leaflets or plumes like those of the Dorididce. We have not been able to 

 detect the ciliary movements on these organs, though we have found cilia in vigorous action 

 along the margin of the foot and on the anal nipple : it is therefore likely that they exist 

 over the whole of the body ; and that they cover both the branchial tufts and branches of 



* From StvSpov, a tree, and vwroq, the hack. 



