160 University of Calif ovnia Puhlicaiions in Zoology [Vol.18 



on the dorsal side of the niembraiious posterior continuation of the 

 levator labialis superioris. The ventral part has its origin on the 

 ventral side of the same membrane ; its direction is the same as in the 

 case of the dorsal fibers and it is inserted on the posterior outer sur- 

 face of the mandible. 



Fig. 4. Hypobrauchial muscles, Heptanchus macidatus, ventral view (XI). 

 hh., basihyoid cartilage; car., coracoarcuales muscle; ch}, first ceratobranchial 

 cartilage; c.hry, first to seveuth coracobranchiales muscles; ch., ceratohyoid 

 cartilage; c.hy., eoracohyoideus muscle; co., eoracoid cartilage; c.md., coraco- 

 mandibularis muscle; (br.'-", first to sixth ventral interbranchial muscles; md., 

 mandibular cartilage. 



2. Adductor arciis hrancJiialis. An adductor, as mentioned before, 

 is absent from the hyoid arch. The dorsal and ventral parts of each 

 of the branchial arches {ad., fig. 2) are drawn together by an adductor 

 arcus branchialis which extends from the epibranchial to the cerato- 

 branchial segments of each arch. The adductors are small and hinge- 

 like and completely fill the angle between the segments. Their origin 



