vou 2, ft. 2.] A TAXONOMIC STUDY OF THE SALPIDAE METCALF. 45 



muscle and all the body muscles are interrupted ventrally (pi. 12, 

 fig. 30). On the right side (pi. 11, fig. 28) the upper end of the inter- 

 mediate muscle bends back in the usual Cyclosalpa manner and unites 

 with the first body muscle, but this union is far down on the side, 

 just above the oral retractor. In fact, the back-turned end of the 

 intermediate muscle fuses with the posterior end of the oral retractor. 

 On the left side (pi. 12, fig. 29) the upper end of the intermediate 

 muscle does not quite reach to the first body muscle, but runs far up 

 dorsally and stops before establishing the connection. It is as if the 

 whole muscle system were so twisted over to the right side that the 

 intermediate muscle on the left side, blocked by the ganglion, fails 

 to reach its proper point of union with the first body muscle, while, 

 on the right side, this attachment is present and by the same lateral 

 twist is pushed ventralward. 



On the right side the first body muscle, in its upper half, unites 

 with both the intermediate muscle and the second body muscle, 

 separating again further dorsally to pass over the actually (morpho- 

 logically ?) mid-dorsal line as a broad band whose breadth suggests 

 that it contains some fibers properly referable to the intermediate 

 muscle. On the left side, muscle I is distinct from both the inter- 

 mediate muscle and body muscle II and does not even come into con- 

 tact with the oral retractor. 



On the right side, body muscle II joins the intermediate muscle and 

 body muscle I above, as already noted, but a little further dorsally 

 it parts company with them and, after a very short free course, unites 

 with the fused muscles III and IV. This union is less perfect than in 

 the case of some other muscles, for the line of demarcation between 

 muscle II and the fused muscles III and IV can be traced through the 

 whole course of their juxtaposition, across the mid-dorsal line, onto 

 the left side. On the left side, muscle II joins the united muscles III 

 and IV, but not the intermediate muscle or body muscle I. Here, 

 again, the impression is that of a shifting of the muscles, over the 

 dorsal surface, toward the right side. 



On the right side, muscle III, in its upper half, is attached to muscle 

 IV, but its fibers are not continued dorsally in union with the latter 

 muscle. On the left side the union of III and IV is more intimate, 

 their fibers passing together across the dorsal surface. 



Muscle IV has its usual position, its ventral ends lying in front of 

 the gut, while the posterior branch passes behind the gut, above the 

 post-abdomen, to unite with its fellow from the opposite side. On the 

 right side, the two parts of this muscle are separated so that the ante- 

 rior branch does not quite touch the band which passes back above the 



