110 U.S. NATIONAL MUSEUM BULLETIN 234 



On the ventral surface of the funnel are 26 hght organs somewhat 

 symmetrically arranged. Most conspicuous of these are (a) a single 

 pair of large light organs arranged transversely slightly above the 

 level of the anterior edge of the funnel member of thelocking apparatus, 

 and (b) a set of three light organs decreasing in size posteriorly and 

 arranged in an oblique row just mediad of the funnel member of the 

 locldng apparatus and directed towards the funnel opening. 



The ventral surface of the head bears five longitudinal series of 

 photophores arranged in distinct lines which cause the surface of the 

 head to appear ridged. The light organs extend onto the arms and 

 their arrangement is as follows: In the midline of the head the median 

 row originates at the edge of the funnel groove and extends forward 

 to the base of the ventral arms. In the midline it consists of two 

 large light organs and eight smaller ones. At the base of the arms 

 this row divides and extends along the angle of the inner edge of the 

 ventral arm to the distal tip. It is composed of irregularly arranged 

 large and small photophores. On each side of the midrow of the 

 head lies a row of mixed photophores which upon the ventral surface 

 of the head is single, but posteriorly it branches in an inverted Y, the 

 inner branch descending deeply into the funnel groove on either side 

 of the bridle, the outer row following the edge of the funnel groove 

 to the origin of the ventral neck fold beside the funnel. Anteriorly, 

 after these two branches unite, the row takes a slight dorsal turn at 

 the base of the ventral arms and extends distally along the median 

 line of the arm to the end. Between the ventrolateral row of photo- 

 phores and the eye lies another row of photophores. Posteriorly it 

 originates at the base of the neck fold anterior to the mantle lock- 

 apparatus. Five or six light organs lie anterior of the neck fold but 

 the row is interrupted, the photophores lacking in the area of clear 

 transparent skin forming the ventral window of the eyeball. Anterior 

 of the window, the row is resumed and extends by means of scattered 

 photophores onto the ventral arm where a distinct and orderly row 

 of organs somewhat widely spaced extend anteriorly on the dorsal 

 membrane to within one-sixth of the length of the arm from the tip. 



The lateral row of light organs appears to divide somewhat at the 

 base of the ventral arms; it furnishes a band which extends onto the 

 ventral side of the ventrolateral arms as a few scattered, deeply 

 sunken organs which extend over about three-fourths of the arm. 

 On the dorsal surface of the arms III are three minute, widely spaced 

 photophores. A single small light organ is located at the base of each 

 of the dorsolateral arms, slightly dorsad. 



Around each eyelid is a circlet of photophores which are crowded 

 ventrally but scattered dorsally. There are 24 around the left eyehd 

 and 27 around the right. 



