ECONOMIC RELATIONS, ANATOMY, AND LIFE HISTORY OF GENUS LERN^A. 1 75 



and Briihl declared that there was none present. If by the term "proboscis" is meant a 

 rigid sucking tube constantly projecting some distance from the ventral surface of the 

 head, Claus and Briihl were right; there is nothing of the sort. But if we may desig- 

 nate as a proboscis the upper and under lips and some of the soft tissue connecting them, 

 which can be protracted and withdrawn at pleasure, then Burmeister and Hartmann 

 were correct, for there is such a proboscis, corresponding in its general make-up to that 

 in the genus Lernceenicus and some other Lemgean genera. 



A careful examination of the musculature connected with this proboscis, as shown 

 in figure 7, leaves no question as to the possibility of its protrusion and withdrawal. 

 (See p. 179.) 



Claus demonstrated a chitin framework supporting the softer parts of the mouth 

 tube in esocina, and this is found also in other species. The dorsal portion of this frame- 

 work is formed by the upper lip, which is comparatively broad and is attached to the 

 front of the head between the bases of the antennae. The rest of the framework con- 

 sists of a narrow chitin ring fused on either side to the lateral margin of the upper lip 

 and supported on the ventral surface by a pair of stout rods, which extend obliquely 

 backwards and outwards in the integument. (See fig. 76, pi. xiv.) The lower lip is in 

 the form of a pad, attached to the outer surface of the mouth tube and articulated with 

 the chitin ring in such a way as to allow of considerable motion backwards and for- 

 wards. This motion is accomplished by four longitudinal muscles, which extend back- 

 wards from the lower lip along the ventral surface. 



The mouth parts. — Inside the mouth tube and between the two lips lie the mandi- 

 bles, each of which is one jointed and strongly curved, with a sharp spinelike point and 

 without teeth. These mandibles were discovered, described, and figured by Claus, but 

 have been overlooked by the other investigators. They are difficult of detection and 

 require the previous removal of the maxillae and maxillipeds before they can be seen. 

 The mandible of variabilis is curved more strongly than that of esocina and is clearly 

 shown in figure 50. 



The first and second maxillae are attached to the outside of the mouth tube between 

 the upper and under lips. Each consists of a stout basal joint and a movable terminal 

 claw; in the first pair the claw is single, in the second pair it is double. Both pairs of 

 maxillae converge inwards across the tip of the mouth tube, so that the claws meet on the 

 median line. (See fig. 5, pi. vi.) 



The maxillipeds originate some distance behind the mouth tube upon the ventral 

 surface of the cephalothorax. Each is made up of an elongated basal joint, which 

 carries on its inner margin at the distal end a papilla tipped with a long plumose seta, 

 and a terminal joint armed with five curved claws and a tuft of setae. The number of 

 parts in these maxillipeds is apparently constant for all the species, the specific dif- 

 ferences being confined to relative shape and size. 



The swimming legs. — There are five pairs of swimming legs which are variously 

 disposed upon the body in the different species. A table has already been published " 

 showing the relative distances between the successive pairs of legs in the North 

 American species, and that table is repeated here with the addition of the two new 

 species. 



a Bulletin, United States Bureau of Fisheries, vol. 34, 1914, p. 370. 



