directed toward the head end the protective layer 200 only has a head portion which fits between the head end of the shell 100 and the head end of the padded cover 300 the protective layer 200 is roughly u shaped in cross section having a flat portion 205 adapted to be beneath the infant 39 s body and two side walls 207 208 on either side of this flat portion 205 like the other components the flat portion 205 contains slots 230 for restraints that register with slots 330 and 130 when the protective layer 200 padded cover 300 and shell 100 are in the assembled condition the protective layer also includes a plurality of crush ribs 240 along both side walls 207 208 these crush ribs 240 may in contact with the exterior shell 100 when in the assembled condition in those sidewall regions between the crush ribs 240 air occupies the space between the protective layer and the exterior shell therefore in those areas where the crush ribs are spaced far apart there is limited direct contact between the protective layer 200 and the exterior shell 100 this causes the protective layer 200 to more readily deform upon impact thereby absorbing a significant amount of the force of impact conversely in those areas where the crush ribs are spaced closer together there is more direct contact between the protective.