BATHYPELAGIC SQUID BATHTTEUTHIS 33 



lateral and posterior borders of the funnel valve with the doreal 

 wall of the funnel tube. 



The head is broad and short (pi. 1). The huge, anteriorly directed 

 eyes give the head a distinctly swollen appearance. The head narrows 

 markedly at the base of the brachial crown just anterior to the eye 

 openings. The dorsal and ventral surfaces of the head are nearly flat 

 and the head tapers anteriorly into the brachial crown. No nuchal 

 crests or folds occur in the region of the neck. 



The nuchal component of the mantle-nuchal locking apparatus 

 is a strong, elongate, cartilaginous structure with a straight median 

 ridge bordered on each side by a smooth sulcus (pi. Ic). The 

 edge of the nuchal component is bordered by a broad membranous 

 skirt. The cartilaginous mantle component of the nuchal lock is com- 

 plementary in structure to the nuchal component. A deep median 

 sulcus is bordered on each side by a long, straight ridge. The mantle 

 component lies directly ventral to the anterior terminus of the gladius, 

 and its form is imposed by the chitinous rhachis that has a deep 

 median groove ventrally and is supported by strong, rodlike edges. 



The olfactory papillae lie on the posterior ventrolateral surface of 

 the head just anterior to the collar. They are short, small, slightly 

 swollen, lobate, or flaplike structures that lie beneath the anterior 

 border of the mantle. 



The integumentary layers on the head are similar to those on the 

 mantle. The gelatinous layer is particularly thick on the dorsal and 

 posterior regions of the head. In general, the pigmentation on the head 

 and arms is more concentrated than it is on the mantle, so that the 

 color is a dark maroon. 



A small, simple photophore is located at the base of each of the first, 

 second, and third arms (pi. 5a, e). No trace of a photophore is present 

 at the bases of the ventral arms. The photophore is readily visible on 

 smaller specimens as a dark, elongate, rounded patch, often with a pale 

 central spot. In larger specimens, however, the light organs become 

 less distinct because they are partially overgrown with integument and 

 gelatinous tissue. The organs arise in one of the deeper chromatophore 

 layers where they are surrounded by an area of maroon pigment which 

 gradually diminishes away from the organ. In long-preserved speci- 

 mens that have become bleached, the pliotophores usually are indis- 

 tinguishable. 



The arms and tentacles extend from the base of the narrow brachial 

 crown. The arms are short, subequal in length. The arm formula occur- 

 ring with the greatest frequency is 4.3.2.1, followed by 4 = 3 = 2.1 and 

 4.3 = 2.1. The length of the arms is measured from the basal portion of 

 the sucker-bearing area to the tip of the arm. The measurement on the 



